google/yamlfmt

What it does

You give it file names, or a folder, and it rewrites each file in a consistent layout. Pointing it at a folder makes it walk through everything inside and pick up files ending in .yaml and .yml. One flag switches on a wider pattern syntax, so you can describe exactly which files to include. A check mode reports what it would change and alters nothing, which is what you run before accepting a change rather than while writing one. Settings go in a .yamlfmt file, and the formatting itself is pluggable, so a different style can be added. It also works as a library inside another program, and there is a container image, so it can run without being installed. Release files carry checksums and are signed, from version 0.14.0 onward. The newest release is v0.21.0, from 5 January 2026, and code landed on 13 October 2026. What it explicitly does not have is official backing. The README states the project is not yet officially supported by Google, and that it is maintained by one person working on it mostly in spare time.

Why it matters

Who it suits. Anyone with a pile of YAML files that several people edit: container settings, build pipelines, deployment descriptions. The check mode is the part that pays for itself, because it ends the argument about indentation by moving it to a program. Skip it if YAML barely appears in your work, or if a general formatter already covers it, because this does one format and nothing else.

Verdict. A good small tool, and the thing to understand is the ownership rather than the code. An account name of google on GitHub tells you who owns the account, not who is on call. This project says in its own README that Google does not officially support it and that one person maintains it in spare time, and nine months between releases is consistent with that. None of this makes it a bad choice, because a formatter that goes quiet still formats. It does mean you should not pick it over an alternative on the strength of the name. prettier/prettier at 52,300 stars formats YAML among many other languages and is the better choice if a project already runs it for JavaScript or Markdown. mikefarah/yq at 15,900 stars is a different job that often gets confused with this one: it reads and edits values inside YAML rather than tidying the layout.