Document ID: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-ca13-19-01918/USCOURTS-ca13-19-01918-0/pdf.json

Parties Involved:
Amazon Web Services, Inc.
Intervenor
Amazon.com, Inc.
Intervenor
BuzzFeed, Inc.
Appellee
Dictionary.com, LLC
Appellee
Level 3 Communications, LLC
Not party
Oath Inc.
Appellee
Patreon, Inc.
Appellee
PersonalWeb Technologies LLC
Appellant
Popsugar Inc.
Appellee
Vice Media, LLC
Appellee
Vox Media, Inc.
Appellee
Ziff Davis, LLC
Appellee

Document Text:

United States Court of Appeals 

for the Federal Circuit ______________________

IN RE: PERSONALWEB TECHNOLOGIES LLC,

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

PATREON, INC.,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

DICTIONARY.COM, LLC,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

Case: 19-1918 Document: 123 Page: 1 Filed: 06/17/2020
2 IN RE: PERSONALWEB TECHNOLOGIES LLC

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

VOX MEDIA, INC.,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

VICE MEDIA, LLC,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Case: 19-1918 Document: 123 Page: 2 Filed: 06/17/2020
IN RE: PERSONALWEB TECHNOLOGIES LLC 3

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

OATH INC.,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

BUZZFEED, INC.,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

Case: 19-1918 Document: 123 Page: 3 Filed: 06/17/2020
4 IN RE: PERSONALWEB TECHNOLOGIES LLC

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

POPSUGAR, INC.,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PERSONALWEB TECHNOLOGIES LLC,

Plaintiff-Appellant

LEVEL 3 COMMUNICATIONS, LLC,

Plaintiff

v.

ZIFF DAVIS, LLC,

Defendant-Appellee

AMAZON.COM, INC., AMAZON WEB SERVICES, 

INC.,

Intervenors

______________________

2019-1918

______________________

Appeal from the United States District Court for the 

Northern District of California in Nos. 5:18-cv-05599-BLF, 

5:18-cv-05606-BLF, 5:18-cv-05969-BLF, 5:18-cv-05970-

BLF, 5:18-cv-06044-BLF, 5:18-cv-06046-BLF, 5:18-cvCase: 19-1918 Document: 123 Page: 4 Filed: 06/17/2020
IN RE: PERSONALWEB TECHNOLOGIES LLC 5

06612-BLF, 5:18-cv-07119-BLF, 5:18-md-02834-BLF, 

United States District Judge Beth Labson Freeman.

______________________

Decided: June 17, 2020 

______________________

MICHAEL AMORY SHERMAN, Stubbs Alderton & 

Markiles LLP, Sherman Oaks, CA, argued for plaintiff-appellant. Also represented by VIVIANA H. BOERO HEDRICK, 

JEFFREY F. GERSH, WESLEY WARREN MONROE, STANLEY 

HUGH THOMPSON, JR.; SANDEEP SETH, SethLaw, Houston, 

TX. 

 J. DAVID HADDEN, Fenwick & West, LLP, Mountain 

View, CA, argued for all defendants-appellees and for intervenors. Defendants-appellees Vox Media, Inc., Vice Media, LLC, Oath Inc., BuzzFeed, Inc., Dictionary.com, LLC, 

Patreon, Inc., Ziff Davis, LLC, Popsugar Inc. and intervenors Amazon.com, Inc., Amazon Web Services, Inc. also 

represented by SAINA S. SHAMILOV, RAVI RAGAVENDRA 

RANGANATH; TODD RICHARD GREGORIAN, San Francisco, 

CA. Defendant-appellee Vice Media, LLC also represented 

by BENJAMIN J. BYER, Davis Wright Tremaine LLP, Seattle, WA; KIMBERLY HERMAN, Sullivan & Worcester, Boston, 

MA; CHRISTOPHER T. MCWHINNEY, Washington, DC. Intervenors Amazon.com, Inc., Amazon Web Services, Inc. 

also represented by JEFFREY H. DEAN, Amazon.com, Inc., 

Seattle, WA.

 ______________________

Before WALLACH, BRYSON, and TARANTO, Circuit Judges.

BRYSON, Circuit Judge.

Appellant PersonalWeb Technologies LLC filed a number of lawsuits charging dozens of customers of Amazon.com, Inc., and Amazon Web Services, Inc., (collectively 

“Amazon”) with infringing several related patents. 

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6 IN RE: PERSONALWEB TECHNOLOGIES LLC

Amazon responded with a declaratory judgment action 

seeking an order declaring that PersonalWeb’s lawsuits 

against Amazon’s customers were barred as a result of a 

prior lawsuit brought by PersonalWeb against Amazon, 

which was dismissed with prejudice. In the eight cases 

that are now on appeal, the district court agreed with Amazon that the consequence of the prior dismissal was to bar 

PersonalWeb’s infringement actions against Amazon’s customers. In re: PersonalWeb Techs., LLC, No. 5:18-md02834-BLF, 2019 WL 1455332 (N.D. Cal. Apr. 2, 2019). We 

affirm.

I

A

There are five patents at issue in this appeal: U.S. Patent Nos. 5,978,791 (“the ’791 patent”), 6,928,442 (“the ’442 

patent”), 7,802,310 (“the ’310 patent”), 7,945,544 (“the ’544 

patent”), and 8,099,420 (“the ’420 patent”) (collectively,

“the True Name patents”). All five patents share a largely 

common specification and claim priority to the same abandoned patent application, which was filed on April 11, 

1995.

According to the specification, there was a problem 

with the way prior art computer networks of the mid-1990s 

identified data in their systems. There was “no direct relationship between the data names” and the contents of the 

data item. ’442 patent, col. 2, ll. 13–14. The same file name 

in two different folders could refer to different data items, 

or two different file names could refer to the same data 

item. Id. at col. 2, ll. 15–17. Consequently, computer networks could become clogged with duplicate data, and the 

efficiency and integrity of data processing systems could be 

impaired. Id. at col. 2, line 30, through col. 3, line 43.

The inventors of the patents in suit purported to solve 

this problem by devising what they referred to as “True 

Names” for data items. Id. at col. 6, ll. 7–11. The True 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 7

Name system created a “substantially unique” identifier 

for each data item that depended only on the content of the 

data itself. Id.; see also id. at col. 3, ll. 30–33. The True 

Name system thus did not depend on other purportedly 

less reliable means of identifying data items, such as userprovided file names.

The common specification of the patents in suit teaches 

that file names in the True Name system can be created 

using a “hash function.” Id. at col. 12, ll. 57–63. A hash

function is a mathematical function that reduces a data 

block of arbitrary size and converts it into a relatively 

small, fixed-length sequence, “such that the True Name of 

the data block is virtually guaranteed to represent the data 

block B and only data block B.” Id.

In the True Name system, a large file is first partitioned into smaller segments. The hash function is then 

applied to each segment. Id. at col. 14, ll. 16–35. The resulting values are strung together, and a hash function is 

applied to the entire string of values, to compute the True 

Name of the large file. Id.

The specification summarizes a variety of applications 

for the True Name invention, including using True Names

(1) to avoid storing multiple copies of a file, when those copies have been assigned different names; (2) to avoid copying 

data from a remote location when a local copy is already 

available; and (3) to verify that data retrieved from a remote location is the data that was intended to be retrieved. 

Id. at col. 3, ll. 49–55; see also id. at col. 4, ll. 25–27.

B

In December 2011, PersonalWeb sued Amazon and one 

of Amazon’s customers, Dropbox, Inc., for patent infringement in the United States District Court for the Eastern 

District of Texas. In the complaint, PersonalWeb alleged 

that “Amazon has infringed and continues to infringe [the 

True Name patents, among others] by its manufacture, 

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8 IN RE: PERSONALWEB TECHNOLOGIES LLC

use, sale, importation, and/or offer for sale of the following 

products and services within the PersonalWeb Patent 

Field: Amazon Simple Storage Service (S3)[.]”

Amazon S3 provides web-based storage to certain customers, typically companies with websites. The customers 

can use S3 to store static content, such as images, for their 

websites. Information that is stored in the S3 system is 

stored in the form of “objects” that are organized into customer-created containers called “buckets.” Once an object 

is stored in S3, it can be made available over the entire Internet.

To use an example featured in Amazon’s brief, if a company creates a webpage containing a picture of a puppy, 

that picture can be stored in S3. When a user visits the 

company’s website, the user’s web browser is directed to 

download the puppy picture from S3 in order to display the

website. The way the user’s web browser asks to download 

the puppy picture from S3 is through a Hyper Text Transfer Protocol (“HTTP”) “GET” request.1

S3 automatically generates an “ETag” for every object 

stored in S3. ETags provide useful identifying information 

about an object. For most objects, S3 creates an ETag by 

running a particular hash function on the object’s content. 

If the object’s content changes, the ETag changes. S3 uses

ETags in several of its operations where it is helpful to 

know that identifying information.

For example, when the user downloads the puppy picture described above from S3, the user’s computer might 

store that picture in the computer’s temporary memory or 

cache. If the user requests the same file again, S3 compares the ETag for the file stored in the user’s cache to the 

1 HTTP is a standard communication protocol that 

web browsers and web servers follow in order to communicate with each other on the Internet.

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IN RE: PERSONALWEB TECHNOLOGIES LLC 9

file stored on S3. If the ETags are identical, S3 responds 

with a status code indicating that the user’s computer already has a copy of the picture, so there is no need to download the picture again. If S3 does not contain a file with 

the same ETag, however, that indicates that the contents 

of the file have been changed. In that event, S3 will send 

the user’s web browser the file containing the updated version of the picture. The parties refer to the request for a 

file in that scenario as a “conditional get request” because 

the operation will be performed only if a certain condition 

is met. PersonalWeb also refers to such conditional get requests as “cache control.” Conditional get requests help 

avoid unnecessary downloads, thereby saving time and 

network bandwidth.

S3 also uses ETags when customers, such as companies 

with websites, upload objects to S3. One method of uploading that S3 supports is what Amazon calls the Multipart 

Upload Application Program Interface. The multipart upload function allows users to upload an object larger than 

five gigabytes as a series of parts. Once all the parts have 

been uploaded, S3 can assemble them into a single object 

for storage. S3 generates an ETag for each uploaded part

as well as for the completed object. The ETags can be used 

to verify that none of the parts were corrupted during the 

upload.

In its infringement contentions in the Texas case, PersonalWeb referenced S3’s use of both multipart upload and 

conditional get requests. The contentions are extensive, 

but they consist mainly of similar and sometimes identical

material repeated numerous times. A commonly appearing 

feature in the infringement contentions is a reference to 

S3’s use of ETags to compare the identity of different objects in order to determine whether or not to perform certain operations. See, e.g., J.A. 1651 (“Amazon S3 causes 

the content-dependent name of the particular data item 

(the ‘ETag’) to be compared to a plurality of values (other 

‘ETags’). . . . When doing GET, HEAD, PUT/COPY 

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10 IN RE: PERSONALWEB TECHNOLOGIES LLC

operation with certain conditional parameters, the existence of the particular item at a particular location is determined with Etag.”); J.A. 1652 (“GetIfMatchEtags uses the 

received Etag attached by the user request and compares 

it with the digest contained in the node for that specific object to determine whether or not access to the object is allowed based upon the match or non-match of hashes.”); J.A. 

1653 (“Upon receiving the parts during multipart upload, 

the user’s list of etags is used to compare with the etags 

that are generated for the parts to check for the correct 

parts before combining the parts.”).

Consistent with its infringement contentions in the 

Texas case, PersonalWeb represented in a discovery motion in that case that S3’s use of ETags to perform conditional operations infringed the True Name patents:

The accused products in this case are Amazon’s 

Simple Storage Service (“S3”) and Amazon Web 

Services, LLC’s Storage Gateway. S3 is a cloud 

storage service, and the accused functionalities of 

S3 include but are not limited to its “multipart upload” feature and “conditional operations.” . . . In 

response to receiving each uploaded part of a file, 

S3 creates an ETag for the part uploaded, which is 

a MD5 hash of the contents of the part. PersonalWeb maintains that S3’s use of these hash values 

infringes the patents-in-suit.

A customer who stores files using S3 is able to 

send a variety of different requests to Amazon, e.g., 

to get a file, to copy a file, or to put a file into storage. The customer can optionally require that the 

operation succeed or fail based on a comparison of 

a user-provided ETag against the ETag S3 has 

stored for the file in question, referred to as “conditional operations.” For example, in S3’s “conditional copy” feature, the two options are “If-Match”

and “If-None-Match”—the former allowing a 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 11

successful copy operation only if the ETags match, 

and the latter only if the ETags do not match. If 

the match succeeds, then the copy operation is allowed to be performed; otherwise, S3 returns an error. PersonalWeb maintains that S3’s conditional 

operations infringe the patents-in-suit.

J.A. 2045–46 (emphasis added).

After the district court issued its claim construction order in the Texas case, PersonalWeb stipulated to the dismissal of all its claims against Amazon with prejudice.2 

Pursuant to that stipulation, the district court in June 

2014 issued an order dismissing all claims against Amazon 

with prejudice; the court subsequently entered final judgment against PersonalWeb.

C

Beginning in January 2018, PersonalWeb filed dozens 

of new lawsuits in various districts against website operators, many of which were Amazon’s customers. PersonalWeb alleged that by using S3, Amazon’s customers had 

infringed the True Name patents.

Amazon intervened in the actions against its customers and undertook the defense of the customer-defendants 

in all the cases now before this court. In addition, Amazon 

filed a declaratory judgment complaint against PersonalWeb, seeking an order barring PersonalWeb’s infringement 

actions against Amazon and its customers based on the 

prior action against Amazon in the Eastern District of 

Texas. The Judicial Panel on Multidistrict Litigation consolidated the customer cases and the Amazon declaratory 

judgment action in a multi-district litigation proceeding, 

2 PersonalWeb had previously dismissed its claims 

against Dropbox, Inc., without prejudice. Dropbox is not a 

party to any of the cases before this court.

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12 IN RE: PERSONALWEB TECHNOLOGIES LLC

and assigned the consolidated cases to the United States 

District Court for the Northern District of California for 

pretrial proceedings. That court decided to proceed with 

the Amazon declaratory judgment action first. Based on 

input from the parties, the court selected one representative customer case (the case against Twitch Interactive, 

Inc.) to proceed along with the Amazon declaratory judgment action. The court stayed all the other customer cases. 

Because PersonalWeb represented that it would not be able 

to proceed in the other customer cases if it lost its case 

against Twitch, the district court relied on PersonalWeb’s 

pleadings against Twitch as being representative of PersonalWeb’s pleadings in the other customer cases.

In its counterclaim against Amazon in the declaratory 

judgment action, PersonalWeb alleged that S3 infringed 

the True Name patents when S3 used ETags to perform 

conditional operations. In particular, PersonalWeb accused S3’s use of ETags to determine whether a customer’s 

web browser should reuse its cached data or download a 

new, updated version of the data. According to PersonalWeb, “Amazon thereby reduced the bandwidth and computation required by its S3 web host servers (acting as origin 

servers for its web server customers) and any intermediate 

cache servers . . . .” J.A. 2929. PersonalWeb made similar 

allegations in its complaints against Amazon’s customers.

PersonalWeb’s infringement contentions tracked the 

complaints against Amazon’s customers. For example, 

PersonalWeb alleged that “[t]he distribution of hosted 

webpage file content (content) to other computers such as 

outside intermediate cache servers and computers running 

web browsers . . . is controlled from an S3 website file host 

server (a first computer). This is done in response to a conditional HTTP GET request (a request) obtained by an S3 

website file host server (a first device in the system) from 

another computer (a second device in the system) . . . .” 

J.A. 381. The conditional HTTP GET requests included 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 13

ETags that, according to PersonalWeb, corresponded to the

claimed “content-dependent name.”

D

Amazon moved for summary judgment in its declaratory judgment action and partial summary judgment in 

PersonalWeb’s infringement action against Twitch. Amazon argued that, in light of the with-prejudice dismissal of 

PersonalWeb’s action against Amazon in the Texas case,

PersonalWeb was barred from suing Amazon or its customers for infringement based on Amazon’s S3 system. 

The district court granted the motion in part. It held 

that claim preclusion barred PersonalWeb’s claims regarding acts of infringement occurring prior to the final judgment in the Texas action, and that the Kessler doctrine, 

first adopted by the Supreme Court in Kessler v. Eldred, 

206 U.S. 285 (1907), barred PersonalWeb’s claims of infringement relating to S3 after the final judgment in the 

Texas action. 

With respect to claim preclusion, the district court held 

that all the requirements of that doctrine were met. First, 

the court determined that the with-prejudice dismissal in 

the Texas action was a final judgment on the merits, and 

that PersonalWeb did not reserve any rights in the stipulated dismissal in that case. In re PersonalWeb, 2019 WL 

1455332, at *6–7. 

Second, the court concluded that Amazon’s customers 

were in privity with Amazon. As the court explained, Amazon and its customers share the same interest in the unfettered use of Amazon’s web services; Amazon adequately 

represented that interest in the Texas action; and Amazon 

agreed to indemnify its customers and assumed the defense of its customers against PersonalWeb’s infringement 

charges. Id. at *7–9. 

Third, the court ruled that the causes of action asserted 

in the Texas case and in the customer cases were the same. 

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14 IN RE: PERSONALWEB TECHNOLOGIES LLC

The court rejected PersonalWeb’s contention that the 

claims against Amazon in the Texas case were limited to 

the multipart upload features of S3, and did not extend to 

S3 generally. Id. at *10–13. The court concluded that “both 

the complaint and the infringement contentions in the 

Texas Action indisputably support the Court’s conclusion 

that the Texas Action asserted infringement against all of 

S3 and was not limited only to [the multipart upload feature].” Id. at *12. Different features of the same product, 

the court ruled, do not give rise to separate causes of action. 

Id. at *13. 

Finally, the court rejected Amazon’s argument that 

claim preclusion applies through the expiration of the patents, and instead concluded that claim preclusion applies 

only up to the date of the final judgment in the Texas action. Id. at *13–14.

With respect to the Kessler doctrine, the district court 

held that the judgment in the Texas case gave rise to a limited trade right to continue producing, using, and selling 

the product at issue in that case “even when the acts of infringement occurred post-final judgment and even when it 

was third parties who allegedly engaged in those acts of 

infringement.” Id. at *15 (internal quotation marks and 

citation omitted). The court rejected PersonalWeb’s argument that the Kessler doctrine is “rooted in . . . issue preclusion” and does not apply because the judgment in the 

Texas case did not specifically adjudicate the issue of noninfringement. Id. at *14–16. 

The district court then determined that its summary 

judgment ruling had the effect of disposing of the eight customer cases in which PersonalWeb alleged infringement 

based solely on the customer’s use of Amazon’s S3 system. 

Accordingly, the court dismissed those eight cases. PersonalWeb appeals from the judgment in those cases.

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IN RE: PERSONALWEB TECHNOLOGIES LLC 15

II

PersonalWeb raises two primary challenges to the district court’s decision. First, PersonalWeb contends that 

claim preclusion is inapplicable to the actions against Amazon’s customers because the Texas case involved a different feature of Amazon’s S3 system, and therefore a 

different cause of action, than the feature that is at issue 

in the customer cases. Second, PersonalWeb contends that

the with-prejudice dismissal of the action against Amazon

in the Texas case did not constitute an adjudication of noninfringement and is therefore insufficient to trigger the

Kessler doctrine.3 We reject both challenges.

A

Under the doctrine of claim preclusion, ‘‘a judgment on 

the merits in a prior suit bars a second suit involving the 

same parties or their privies based on the same cause of 

action.” Parklane Hosiery Co. v. Shore, 439 U.S. 322, 326

n.5 (1979). Claim preclusion bars both those claims that 

were brought as well as those that could have been brought 

in the earlier lawsuit. Lucky Brand Dungarees, Inc. v. 

Marcel Fashions Grp., Inc., 140 S. Ct. 1589, 1594–95 

(2020); Brain Life, LLC v. Elekta Inc., 746 F.3d 1045, 1053 

(Fed. Cir. 2014); Owens v. Kaiser Found. Health Plan, Inc., 

244 F.3d 708, 713 (9th Cir. 2001).

3 In the trial court, PersonalWeb also contended that 

claim preclusion applies only up to the date of the operative 

complaint in the prior action. PersonalWeb has not challenged the trial court’s ruling that “claim preclusion bars 

PersonalWeb’s claims through the date of the final judgment in the Texas Action.” In re PersonalWeb, 2019 WL 

1455332, at *13. Because PersonalWeb has not appealed 

that aspect of the trial court’s decision, we do not address 

it.

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16 IN RE: PERSONALWEB TECHNOLOGIES LLC

To the extent that a case turns on general principles of 

claim preclusion, as opposed to a rule of law having special 

application to patent cases, this court applies the law of the 

regional circuit in which the district court sits—here the 

Ninth Circuit. Acumed LLC v. Stryker Corp., 525 F.3d 

1319, 1323 (Fed. Cir. 2008). However, the question 

whether two causes of action for patent infringement are 

the same is an issue peculiar to patent law, and we therefore analyze that issue under Federal Circuit law. Id.

For purposes of claim preclusion, PersonalWeb does 

not dispute the district court’s ruling that the with-prejudice judgment in the Texas case is a final judgment on the 

merits. PersonalWeb also does not challenge the district 

court’s determination that Amazon and its customers are 

in privity, and thus are regarded as the same parties for 

claim preclusion purposes. The sole basis for PersonalWeb’s challenge to the district court’s finding on claim preclusion is its contention that the Texas action and the 

customer suits involved different causes of action. 

In determining whether causes of action for patent infringement are the same, we are guided by the Restatement (Second) of Judgments (1982). See SimpleAir, Inc. v. 

Google LLC, 884 F.3d 1160, 1165 (Fed. Cir. 2018); Acumed, 

525 F.3d at 1323–24. Following the approach taken in the

Restatement, we define a cause of action by the transactional facts from which it arises, and we consider the extent 

of the factual overlap between the two alleged claims at issue. See Gillig v. Nike, Inc., 602 F.3d 1354, 1363 (Fed. Cir.

2010) (“Claims arising from the same nucleus of operative 

facts are barred by res judicata.”); Senju Pharm. Co. v. Apotex Inc., 746 F.3d 1344, 1349 (Fed. Cir. 2014); Acumed, 525 

F.3d at 1323–24 (citing Restatement § 24); Foster v. Hallco 

Mfg. Co., 947 F.2d 469, 478 (Fed. Cir. 1991) (noting that a 

“claim,” i.e., a cause of action, “is used in the sense of the 

facts giving rise to the suit”).

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IN RE: PERSONALWEB TECHNOLOGIES LLC 17

In patent cases, one of the areas of factual overlap we 

consider “is the overlap of the product or process accused in 

the instant action with the product or process accused in 

the prior action.” Senju, 746 F.3d at 1349. Claim preclusion does not apply unless the products or processes are essentially the same. Id. (citing Acumed, 525 F.3d at 1324); 

SimpleAir, 884 F.3d at 1167. “Accused devices are ‘essentially the same’ where the differences between them are 

merely ‘colorable’ or ‘unrelated to the limitations in the 

claim of the patent.”’ Acumed, 525 F.3d at 1324 (quoting 

Foster, 947 F.2d at 480). We also consider whether the 

same patents are involved in both suits. Senju, 746 F.3d 

at 1349.

Importantly, under well-settled principles of claim preclusion, different arguments or assertions in support of liability do not all constitute separate claims. See Foster, 

947 F.2d at 478. Regardless of the number of substantive 

theories available to a party and regardless of the differences in the evidence needed to support each of those theories, a party may not split a single claim into separate 

grounds of recovery and raise those separate grounds in 

successive lawsuits. See Mars Inc. v. Nippon Conlux Kabushiki-Kaisha, 58 F.3d 616, 619 (Fed. Cir. 1995); Restatement § 24 cmt. a. Rather, the party must raise in a single 

lawsuit all the grounds of recovery arising from a particular transaction that it wishes to pursue. Mars, 58 F.3d at

619. 

PersonalWeb asserts that in the Texas case it accused 

only the multipart upload functionality of Amazon’s S3 system. In the customer cases before the California court, PersonalWeb contends it has accused the “cache control”

functionality, an entirely different feature of Amazon’s S3

system. According to PersonalWeb, these different features constitute different products or processes for 

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18 IN RE: PERSONALWEB TECHNOLOGIES LLC

purposes of claim preclusion analysis.4 PersonalWeb thus 

contends that the accused activity in the customer cases is 

not essentially the same as the activity that was accused in 

the Texas case, and that claim preclusion is therefore inapplicable in the customer cases.

Although PersonalWeb contends that the accused feature in the customer cases is different from the accused feature in the Texas case, PersonalWeb concedes that “the 

conditional GET commands” that are at issue in the customer cases were identified in the infringement contentions in the Texas case. Appellant’s Br. at 37. Nonetheless, 

PersonalWeb contends that there were only a “handful” of 

references to those conditional operations in the Texas infringement contentions, not enough to constitute a substantial factual overlap. Moreover, PersonalWeb contends 

that it referred to that infringement theory in the Texas 

case only by way of “analogy.”

Contrary to PersonalWeb’s assertions, PersonalWeb 

did not limit its infringement contentions in the Texas case 

to S3’s multipart upload functionality. As PersonalWeb 

told the trial court in the Texas case, “the accused functionalities of S3 include but are not limited to its ‘multipart upload’ feature and ‘conditional operations.’” PersonalWeb’s 

assertion that it included conditional get requests in the 

Texas infringement contentions as analogies, not accusations, is thus at odds with the representations PersonalWeb made in the Texas case. Because PersonalWeb 

accused the use of “conditional operations” in the Texas 

case, PersonalWeb’s arguments regarding the purported 

4 PersonalWeb also contends that the customer cases 

are different because they include a new product, Amazon 

CloudFront. None of the customer cases before this court, 

however, involve accusations against CloudFront, so that 

argument is irrelevant to the resolution of this appeal.

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IN RE: PERSONALWEB TECHNOLOGIES LLC 19

differences between the multipart upload and the “cache 

control” functionalities of S3 are irrelevant.

In any event, regardless of the breadth of the specific 

infringement theories PersonalWeb pursued in the Texas 

case, it is clear that the complaints in the customer cases 

and the complaint in the Texas case relate to the same set 

of transactions. In the Texas case, PersonalWeb alleged 

that it had been injured by acts of infringement consisting 

of the manufacture, use, sale, importation, and/or offer for 

sale of the Amazon S3 product. Every alleged act of infringement in the eight customer cases before us is likewise 

based on the use of the same Amazon S3 product.

At most, PersonalWeb has shown that it emphasized 

different facts in support of a different theory of infringement in the prior case. But that is not enough to avoid 

claim preclusion. See Restatement § 24 cmt. c (“That a 

number of different legal theories casting liability on an actor may apply to a given episode does not create multiple 

transactions and hence multiple claims. This remains true 

although the several legal theories depend on different 

shadings of the facts, or would emphasize different elements of the facts . . . .”). We therefore uphold the district 

court’s ruling that claim preclusion principles bar PersonalWeb from pursuing infringement claims in the eight customer cases for actions predating the judgment in the 

Texas case.

B

In addition to the two traditional pillars of preclusion 

law—claim and issue preclusion—there is a separate and 

less frequently invoked doctrine that derives from the Supreme Court’s decision in Kessler v. Eldred. We have generally held that claim preclusion cannot apply to acts of 

alleged infringement that occur after the final judgment in 

the earlier suit. See Brain Life, 746 F.3d at 1054; see also 

Dow Chem. Co. v. Nova Chems. Corp. (Canada), 803 F.3d 

620, 626 (Fed. Cir. 2015) (“It is well-established that, as to

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20 IN RE: PERSONALWEB TECHNOLOGIES LLC

claims for continuing conduct after the complaint is filed, 

each period constitutes a separate claim.” (citations omitted)). Likewise, if the requirements of issue preclusion are 

not satisfied, relief under that doctrine will not be available 

to protect post-judgment activity. Brain Life, 746 F.3d 

at 1056. The Kessler doctrine, however, “fills the gap” left 

by claim and issue preclusion, by “allowing an adjudged 

non-infringer to avoid repeated harassment for continuing 

its business as usual post-final judgment in a patent action 

where circumstances justify that result.” Id.

PersonalWeb contends that the Kessler doctrine does 

not apply in this case because Amazon is not an “adjudged 

non-infringer.” In particular, PersonalWeb contends that

the Kessler doctrine is based on principles of collateral estoppel, and that the doctrine therefore cannot be invoked 

unless the issue of infringement or invalidity was “actually 

litigated” in the prior case. PersonalWeb contends that “no 

issues” were actually litigated in the Texas case because 

PersonalWeb dismissed its claims before there was any adjudication.

We have previously addressed whether the Kessler doctrine precludes relitigation only of issues that were actually litigated in a prior action, albeit in slightly different 

contexts. In Brain Life, we explained that the Kessler doctrine barred all claims that were brought or “could have 

been brought” in the prior action. Brain Life, 746 F.3d 

at 1058–59; see also 18 Charles A. Wright et al., Federal 

Practice & Procedure § 4409 & n.34 (3d ed. 2020 update) 

(characterizing Brain Life as utilizing the Kessler doctrine 

as a “substitute for claim preclusion” to bar claims against 

“conduct that the parties reasonably should expect to continue without change”). Similarly, in SpeedTrack, Inc. v. 

Office Depot, Inc., we explained that

the Kessler doctrine is a necessary supplement to 

issue and claim preclusion: without it, a patent 

owner could sue a manufacturer for literal 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 21

infringement and, if unsuccessful, file suit against 

the manufacturer’s customers under . . . any [patent] claim or theory not actually litigated against 

the manufacturer as long as it challenged only 

those acts of infringement that post-dated the judgment in the first action. That result would authorize the type of harassment the Supreme Court 

sought to prevent in Kessler when it recognized 

that follow-on suits against customers could destroy the manufacturer’s judgment right. 

791 F.3d 1317, 1328 (Fed. Cir. 2015).

Likewise, in SimpleAir we said that the Kessler doctrine serves to fill the “temporal gap” left by claim preclusion, even if that gap is not filled by issue preclusion. 884 

F.3d at 1170. As Brain Life, SpeedTrack, and SimpleAir

illustrate, we have treated the Kessler doctrine as a close 

relative to claim preclusion, without its temporal limitation, rather than as an early version of non-mutual collateral estoppel, as PersonalWeb characterizes it. 

None of the other cases PersonalWeb cites requires 

that issues of noninfringement or invalidity be actually litigated before the Kessler doctrine can be invoked. In MGA, 

Inc. v. General Motors Corp., we said that “in its effect,” the 

Kessler doctrine may be compared to defensive collateral 

estoppel. 827 F.2d 729, 734 (Fed. Cir. 1987). PersonalWeb

relies on that statement in an effort to confine the Kessler

doctrine to instances in which collateral estoppel would apply. But PersonalWeb’s reliance on that statement from 

MGA is misplaced. The question presented in MGA was 

whether Michigan state courts would have applied the 

Kessler doctrine. Id. at 733. We concluded that they would 

do so because the Kessler doctrine was sufficiently similar 

to the collateral estoppel law applied by Michigan state 

courts at the time. Id. at 734 (“[W]e discern from a review 

of the law of the state of Michigan, that its courts would 

apply the Kessler doctrine, which in its effect may be 

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22 IN RE: PERSONALWEB TECHNOLOGIES LLC

compared to defensive collateral estoppel[.]”). As our subsequent decisions interpreting MGA demonstrate, however, nothing we said in MGA limited Kessler to requiring 

that the issue of noninfringement or invalidity be “actually 

litigated,” as PersonalWeb contends. See Brain Life, 746 

F.3d at 1058–59; SpeedTrack, 791 F.3d at 1328.

Nor does Mentor Graphics Corp. v. EVE-USA, Inc., 851 

F.3d 1275 (Fed. Cir. 2017), impose such a requirement. In 

that case, Mentor sued EVE for patent infringement. The 

parties subsequently settled the case, with EVE taking a 

license to the patents. Following the licensing agreement 

and settlement, the trial court dismissed Mentor’s claims 

with prejudice. Id. at 1297–98. Later, however, the licensing agreement was terminated. Id. at 1298. When Mentor 

sought to bring a second infringement action, EVE argued 

that the Kessler doctrine barred the lawsuit. We disagreed 

and held that the Kessler doctrine did not bar the second 

lawsuit against EVE over actions that took place after the 

termination of the license. Although the first suit was dismissed with prejudice, we noted that EVE was a willing 

licensee, not an adjudicated non-infringer. Id. at 1301. 

Under those circumstances, we held that Kessler did not 

permit EVE to infringe the patents with impunity after the 

license was no longer in effect. Id.

The with-prejudice dismissal of PersonalWeb’s action 

against Amazon in the Texas case is quite different from 

the licensing agreement that ended the first action in the 

Mentor case. The dismissal in Mentor was contingent on 

the license; when the license was terminated, the contingency disappeared, and Mentor was free to re-initiate its 

infringement action. In this case, by contrast, there was no 

contingency attached to the with-prejudice dismissal to 

which PersonalWeb stipulated.5 PersonalWeb abandoned 

5 PersonalWeb points to a provision in the stipulation and order of dismissal in the Texas case providing that 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 23

its claims against Amazon without reservation, explicit or 

implicit. The judgment in that case therefore stands as an 

adjudication that Amazon was not liable for the acts of infringement alleged by PersonalWeb.

The policy that drove the Supreme Court’s decision in 

Kessler would be ill-served by adopting the rule proposed 

by PersonalWeb. The Court in Kessler recognized that 

even if a manufacturer of goods were to prevail in a patent 

infringement suit, the manufacturer could be deprived of 

the benefits of its victory if the patentee were free to sue 

the manufacturer’s customers. The Court asked rhetorically whether, after Kessler had earned, “by virtue of the 

judgment, the right to sell his wares freely, without hindrance from Eldred [the patentee], must Kessler stand by 

and see that right violated . . . ?” Kessler, 206 U.S. at 289. 

To allow follow-up suits by the patentee against Kessler’s 

customers, the Court explained, “will be practically to destroy Kessler’s judgment right.” Id. at 289–90. Accordingly, the Court concluded that, setting aside “any rights 

which Kessler’s customers have or may have, it is Kessler’s 

right that those customers should, in respect of the articles 

before the court in the previous judgment, be let alone by 

Eldred, and it is Eldred’s duty to let them alone.” Id.

at 289. As the Court put the matter a few years after Kessler, a party that obtains a final adjudication in its favor obtains “the right to have that which it lawfully produces 

Amazon retains “the right to challenge validity, infringement, and/or enforceability of the patents-in-suit via defense or otherwise, in any future suit or proceeding” and 

suggests that the language in question somehow limits the 

preclusive effect of the dismissal. Appellant’s Reply Br. at 

10 (quoting J.A. 335). That is plainly not so. The proviso 

protects Amazon, not PersonalWeb, and therefore does not 

in any way qualify the effect of the with-prejudice dismissal 

of PersonalWeb’s claims in the Texas case. 

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24 IN RE: PERSONALWEB TECHNOLOGIES LLC

freely bought and sold without restraint or interference.” 

Rubber Tire Wheel Co. v. Goodyear Tire & Rubber Co., 

232 U.S. 413, 418 (1914); see also SpeedTrack, 791 F.3d 

at 1323.

Based on the Supreme Court’s analysis in Kessler and 

Rubber Tire Wheel, we have characterized the Kessler doctrine as granting a “limited trade right” that attaches to 

the product itself. SpeedTrack, 791 F.3d at 1323 (quoting

MGA, 827 F.2d at 734–35). The scope of that right is not 

limited to cases involving a finding of non-infringement 

that was necessary to the resolution of an earlier lawsuit, 

but extends to protect any products as to which the manufacturer established a right not to be sued for infringement. 

For that reason, the judgment in the Texas case, pursuant 

to a with-prejudice dismissal, protected Amazon’s S3 product from subsequent infringement challenges, even when 

those challenges were directed at Amazon’s customers rather than at Amazon itself. 

Under PersonalWeb’s narrower construction of the 

Kessler doctrine, a final, adverse disposition of a patentee’s 

claims against the manufacturer of a particular product 

would not give the manufacturer protection from infringement actions against its customers for the use of the same 

product, unless the adverse decision was accompanied by a 

specific, contested adjudication of non-infringement. Such 

a proposition would leave the patentee free to engage in the 

same type of harassment that the Supreme Court sought 

to prevent in Kessler, a result that would be inconsistent 

both with Kessler itself and with this court’s cases interpreting Kessler. See Kessler, 206 U.S. at 289–90; SpeedTrack, 791 F.3d at 1328–29; Brain Life, 746 F.3d at 1056, 

1058–59. 

We do not agree with PersonalWeb’s contention that 

applying Kessler to voluntary dismissals with prejudice 

would contravene the public interest in the settlement of 

patent litigation. See Foster, 947 F.2d at 477 (“[T]he 

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IN RE: PERSONALWEB TECHNOLOGIES LLC 25

Federal Circuit has repeatedly expressed the view that 

there is a strong public interest in settlement of patent litigation.”). Contrary to PersonalWeb’s assertions, the rule 

we apply here will not interfere with the ability of parties 

to resolve patent disputes. To the extent that a plaintiff 

wishes to settle an infringement action while preserving its 

rights to sue the same or other parties in the future, it can 

do so by framing the dismissal agreement to preserve any 

such rights that the defendant is willing to agree to. Settling parties will remain free to limit the preclusive effect 

of a dismissal; they simply have to fashion their agreement 

in a way that makes clear any limitations to which they 

wish to agree as to the downstream effect of the dismissal. 

See, e.g., Hallco Mfg. Co. v. Foster, 256 F.3d 1290, 1295 

(Fed. Cir. 2001); Pactiv Corp. v. Dow Chem. Co., 449 F.3d 

1227, 1231 (Fed. Cir. 2006).

We therefore reject PersonalWeb’s contention that the 

issue of non-infringement must be “actually litigated” in 

order to invoke the Kessler doctrine. PersonalWeb’s stipulated dismissal with prejudice in the Texas case operated 

as an adjudication on the merits for claim preclusion purposes. Levi Strauss & Co. v. Abercrombie & Fitch Trading 

Co., 719 F.3d 1367, 1372–73 (Fed. Cir. 2013) (citing 18A 

Charles A. Wright et al., Federal Practice and Procedure

§ 4435 (2d ed. 2002)). That is, the with-prejudice dismissal 

resolved the dispute about liability for the alleged patent 

infringement that gave rise to the Texas action. Thus, the

dismissal operated as an adjudication of non-liability for 

infringement for purposes of invoking the Kessler doctrine. 

Under that doctrine, the stipulated dismissal with prejudice conferred upon Amazon a limited trade right to continue producing, using, and selling Amazon S3 without 

further harassment from PersonalWeb, either directly or 

through suits against Amazon’s customers for using that 

product.

AFFIRMED

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