Chromium

Chromium version numbers consist of 4 parts: MAJOR.MINOR.BUILD.PATCH.

• MAJOR and MINOR may get updated with any significant Google Chrome release (Beta or Stable update). MAJOR must get updated for any backwards incompatible user data change (since this data survives updates).
• BUILD must get updated whenever a release candidate is built from the current trunk (at least weekly for Dev channel release candidates). The BUILD number is an ever-increasing number representing a point in time of the Chromium trunk.
• PATCH must get updated whenever a release candidate is built from the BUILD branch.

MAJOR and MINOR track updates to the Google Chrome stable channel. In this sense, they reflect a scheduling or marketing decision rather than anything about the code itself. These numbers are generally only significant for tracking milestones. In the event that we get a significant release vehicle for Chromium code other than Google Chrome, we can revisit the versioning scheme.

The BUILD and PATCH numbers together are the canonical representation of what code is in a given release. The BUILD number is always increasing as the source code trunk advances, so build 180 is always newer code than build 177. The PATCH number is always increasing for a given BUILD. Developers and testers generally refer to an instance of the product (Chromium or Google Chrome) as BUILD.PATCH. It is the shortest unambiguous name for a build.

For example, the 154 branch was originally released as 0.3.154.9, but now stands at 1.0.154.65. It's the same basic code with a lot of bug fixes applied. The fact that it went from a Beta release to several 1.0 stable releases just reflects the decision to call some version (1.0.154.36) 'out of Beta'.

Chromium OS

Starting with the R16 release, we standardized on the following: [Chrome Version.]<TIP_BUILD>.<BRANCH_BUILD>.<BRANCH_BRANCH_BUILD>

• The Chromium version is implicit.  On the R25 branch, Chromium OS will be using Chromium version 25.
• TIP_BUILD will be updated every time the canaries run on the tip of tree (trunk/master in various VCS schemas).  This is typically done every 6 hours.  The number increases monotonically.
• BRANCH_BUILD will be updated every time a new build is started on a branch.  This happens whenever a commit is made to the branch.
• BRANCH_BRANCH_BUILD is used when a branch of a branch is made.  This is a bit uncommon, but has happened.  It follows the same rules as BRANCH_BUILD.

An example Chromium OS version string:

• Version 25.0.1364.126
• This is the Chromium version (see previous section for details)
• Platform 3428.193.0 (Official Build) stable-channel stumpy
• This was branched from the tip of tree (ToT) when it was at 3428.0.0.  It is the 193rd build on that branch.

Coordinating Versions

You can use the online CrOS-OmahaProxy app engine to see what versions of Chrome shipped in which versions of Chrome OS.

Alternatively, all releases of Chrome are tagged in the chromeos/manifest-versions.git repository. Follow the same steps as above w/Chromium.