Company: CALX
Filing Date: 2025-07-22
Form Type: S-8
Source: 0001406666-25-000036
Chunk: 0

Company: CALIX, INC
Filing Date: 2025-07-22
Form: S-8
Chunk 0
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<div align='center'>As filed with the Securities and Exchange Commission on July 22, 2025</div>

#### Registration No. 333-

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### WASHINGTON, D.C. 20549

#### FORM S-8

### REGISTRATION STATEMENT

#### UNDER

#### THE SECURITIES ACT OF 1933

#### CALIX, INC.
<div align='center'>(Exact Name of Registrant as Specified in Its Charter)</div>

| Delaware                        |     | 68-0438710            |
| (State or Other Jurisdiction of 
 Incorporation or Organization)  |     | -I.R.S. Employer      
 Identification Number |

#### 2777 Orchard Parkway

#### San Jose, CA 95134
<div align='center'>(Address of Principal Executive Offices including Zip Code)</div>

| Calix, Inc. Fourth Amended and Restated 2019 Equity Incentive Award Plan 
 Calix, Inc. Stock Purchase and Matching Plan                             |

<div align='center'>(Full Title of the Plan)</div>

| Michael Weening                       
 President and Chief Executive Officer 
 Calix, Inc.                           
 2777 Orchard Parkway                  
 San Jose, CA 95134                    
 (408) 514-3000                        |

| (Name and Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service) |

| Copy To:                     
 Kathleen M. Wells, Esq.      
 Latham & Watkins LLP         
 140 Scott Drive              
 Menlo Park, California 94025 |

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definition of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act. Check one:

| Large accelerated filer |     | ý |     | Accelerated filer         |     | ¨ |
| Non-accelerated filer   |     | ¨ |     | Smaller reporting company |     | ¨ |
|                         |     |   |     | Emerging growth company   |     | ¨ |

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any