YAML Linter Alternatives
yamllint, Prettier, and YAMLToolbox serve different jobs. Here is how to pick the right one.
Quick summary
| Tool | Best for | Limitation |
|---|---|---|
| yamllint | CI pipelines, style rules | CLI only; reports errors but does not fix them |
| Prettier | Formatting valid YAML in a project | Rejects broken YAML; no frontmatter awareness |
| YAMLToolbox | Browser validation + frontmatter repair | Not a CI plugin; no custom style rules |
yamllint
Use it when: you want configurable style rules in a CI pipeline — indentation width, truthy values, line length, key ordering, and more.
Where it falls short: it is a command-line linter. It tells you what is wrong but does not repair the file. It also treats a Markdown note with front matter as a YAML error, because it does not separate the --- block from the body.
Prettier
Use it when: you already use Prettier in a JavaScript/TypeScript project and want consistent formatting across languages.
Where it falls short: Prettier formats valid YAML. If the file has a syntax error, it stops and reports the error. It will not fix indentation, trailing whitespace, or missing colon spaces for you. It also does not understand front matter inside Markdown.
YAMLToolbox
Use it when: you need a quick, private, browser-based check, especially for Markdown notes with front matter.
Where it differs: the Frontmatter Validator & Fixer isolates the --- block, ignores the Markdown body, and runs conservative auto-repairs on common mistakes:
- Missing space after a colon
- Trailing whitespace
- Missing closing
--- - Duplicate keys
- Unquoted
yes/no/on/off - Leading-zero numbers
After each fix, it shows a list of exactly what changed, so you can verify nothing was silently altered.
Which should you choose?
- CI / automated checks: yamllint
- Project formatting: Prettier
- Quick browser check or frontmatter repair: YAMLToolbox
Try the frontmatter difference
Paste a full Obsidian or Jekyll note into YAMLToolbox's frontmatter fixer, then try the same text in yamllint or Prettier. Only YAMLToolbox validates the metadata block and ignores the Markdown body.