[Google Chromecast] bhiga:
First ask yourself, do I need to root? Then come back to see if you have possibility to root.

See: Root Mini-FAQ: What's the big deal with root? and Why should I root?

For help with FlashCast, see the FlashCast: Quickly and easily mod your Chromecast thread and Rooting with FlashCast Mini-FAQ

For help with HubCap, see the HubCap Chromecast Root Release! thread.

For help with Flashcast-AutoRoot, see the Flashcast-AutoRoot thread.

Note: THANK YOU to all the folks who contributed reports to the first incarnation of this list. Your help made it possible for many other users to pick winners from their local stores. Now that we're in the second generation of root (and unrootability), it was time for a revamp.

At the core, it's not the serial number that determines whether a Chromecast is rootable, but rather the firmware build on it. However, because Chromecasts ship from the factory with a specific firmware build, we can use the serial number to predict whether a particular unit is rootable out of the box, or is unrootable because it has a firmware that is not vulnerable to known exploits.

Firmware builds >= 19084 are

not

rootable by current means.

Also, for Chromecast, "root" means to flash a rooted ROM that disables Google OTA updates. Any Google OTA update at this point will render a Chromecast unrootable, regardless of its serial number. If that didn't make sense, please reread the previous paragraph above.

Want root? Find your scenario below:

I KNOW MY FIRMWARE BUILD AND IT IS...

12072

-> Root with FlashCast or HubCap 12940 version

Greater than 12072, but less than 19084

-> Try root with HubCap 12940 version, if that doesn't work, try root with HubCap 16664 version

19084 or higher

-> Sorry, you're not rootable

I DON'T KNOW MY FIRMWARE BUILD BUT MY CHROMECAST IS...

NEW, UNOPENED, NOT USED, NOT REFURBISHED, NOT RECERTIFIED, NOT REPLACEMENT

AND

NEVER CONNECTED TO INTERNET

AND ITS SERIAL NUMBER STARTS WITH...

3922 or lower (ie, 38AD, 371C, 3612, etc)

-> Root with FlashCast or HubCap 12940 version

3923 or 3924

-> Please determine your firmware build version without setting up and report it to me with your serial number before attempting root.

-> Build 12072 - Try root with FlashCast

-> Build less than 16664 - Try root with HubCap 12940 version

-> Build greater than 16664 but less than 19084 - Try root with HubCap 16664 version

-> Build 19084 or greater - you're not rootable. Are you sure you didn't get a used/refurbished/recertified/replacement unit??

3925-4A1F (MFG 10/2014 and earlier, or no MFG date on label)

-> Try root with HubCap 12940 version, if that doesn't work, try root with HubCap 16664 version

4A20-4B20 (MFG 9/2014 to MFG 11/2014)

Note: This range is in flux - I have a 4A27 that had 15098 and another user had a 4A29 with 15098, but one user had an unrootable 4A20 with 20472

-> Please determine your firmware build version without setting up and report it to me with your serial number before attempting root.

-> Try root with HubCap 12940 version, if that doesn't work, try root with HubCap 16664 version

4B21 and higher (MFG 11/2014 and newer)

-> Your Chromecast has firmware 20472 or newer and is not rootable.

-> If you determine your firmware build version without setting up is less than 20472, please report it to me with your serial.

SET UP BUT (CONTINUOUSLY) DISCONNECTED FROM INTERNET PRIOR TO AUGUST 1, 2013

-> Root with FlashCast or HubCap 12940 version

SET UP BUT (CONTINUOUSLY) DISCONNECTED FROM INTERNET PRIOR TO SEPTEMBER 4, 2014

-> Try root with HubCap 12940 version, if that doesn't work, try root with HubCap 16664 version

SET UP AND CONNECTED TO THE INTERNET SEPTEMBER 4, 2014 OR LATER

-> Your Chromecast auto-updated to firmware 19084 or newer and is not rootable.

REFURBISHED/RECERTIFIED/REPLACEMENT

-> Impossible to determine what build will be on the device.

-> Determine your firmware build version without setting up then proceed based on build number.

-> Build 12072 - Try root with FlashCast

-> Build less than 16664 - Try root with HubCap 12940 version

-> Build greater than 16664 but less than 19084 - Try root with HubCap 16664 version

-> Build 19084 or greater - you're not rootable.

Root method requirements:

FlashCast method

Firmware build 12072 (this exact build, no others) on Chromecast

Powered MicroUSB OTG cable

Compatible USB flash drive 256 MB or larger (most drives are compatible, a few are not, check the thread)

HubCap method

Firmware build 19084 or lower/older on Chromecast

Powered MicroUSB OTG cable

Teensy 2, Teensy 2++, compatible or similar device that has ported build (see the thread)

Compatible USB flash drive 256 MB or larger (most drives should be compatible, check the thread)

After you already have root via one of the above methods, you can install Flashcast-AutoRoot to stay current with updates while still preserving root.