ryl

ryl is a fast YAML linter and formatter written in Rust. It checks YAML style, applies safe lint fixes, and formats files with configurable layout. It is usable today, but edge-case behaviour is still maturing.

Full documentation lives at https://ryl-docs.pages.dev/.

ryl targets YAML 1.2. See YAML version compatibility for how version directives and implicit types affect linting and formatting.

Coming from yamllint? See the migration guide.

Quick start

ryl enables no rules by default, so it needs a configuration or --enable that turns rules on. --enable ALL runs every rule for a one-off run, and --enable <RULES> runs just the named rules; for a project, drop a .ryl.toml at the root (see Configuration).

ryl check is the lint subcommand and the recommended form; ryl format is the formatter. Bare ryl <paths> still lints identically but is deprecated: it prints a warning to stderr (silenced by --no-warnings) and a later release will remove it, so prefer ryl check.

# Using uv (Python)
uvx ryl check --enable ALL .

# Using npx (Node.js)
npx @owenlamont/ryl check --enable ALL .

# Format in place, or check formatting in CI
uvx ryl format .
uvx ryl format --check .

For prek / pre-commit integration, see ryl-pre-commit.

Installation

uv tool install ryl                 # uv
npm install -g @owenlamont/ryl      # npm
pip install ryl                     # pip
cargo install ryl                   # cargo
pixi global install ryl             # conda-forge
winget install owenlamont.ryl       # winget (Windows)

Building from source (cargo install, or a pip sdist) needs Rust 1.99.0 or newer. The prebuilt wheels, npm, conda-forge and winget packages do not.

Status and scope

• ryl format formats YAML in place without enabling lint rules. Its --check and --diff modes preview changes without writing; [format] in TOML controls the style. It also formats embedded YAML in Markdown with --markdown.
• ryl includes 27 rules, including tags, merge-keys, block-scalar-chomping, and unicode-line-breaks. The rule reference and per-rule pages are at https://ryl-docs.pages.dev/rules/.
• Auto-fixing (--fix) is supported for braces, brackets, colons, commas, comments, comments-indentation, document-end, document-start, empty-lines, hyphens, key-ordering, new-line-at-end-of-file, new-lines, quoted-strings, trailing-spaces, and truthy (case only, e.g. True to true). The set of rules that may apply fixes is configurable via the TOML lint.fixable/lint.unfixable keys.
• --diff previews those safe fixes as a unified diff on stdout instead of writing them (modelled on ruff check --diff); it is mutually exclusive with --fix, works with stdin, and exits 1 iff some file would change.
• TOML is the recommended configuration format and supports the lint.fixable/lint.unfixable fix policy, [lint.per-file-ignores], and rule options such as allow-double-quotes-for-escaping.
• TOML assigns each file a source kind via the [files] table (yaml = [...], markdown = [...]). The legacy yaml-files key is YAML-only; in TOML use [files].yaml.
• YAML embedded in Markdown (front matter and fenced yaml/yml blocks) can be linted by listing globs under [files].markdown; diagnostics map back to the Markdown file. It is off by default; --fix writes safe fixes back into the embedded blocks and --diff previews them at the host-file level. See https://ryl-docs.pages.dev/markdown/.
• YAML configuration (.yamllint, .yamllint.yml, .yamllint.yaml, including the default, relaxed, and empty presets via extends) still works but is deprecated and warns; convert it with ryl --migrate-configs --migrate-write.
• --list-files prints the files ryl would lint (after ignores and config discovery) and exits, without running rules. --no-warnings suppresses warning-level diagnostics in the output. --strict turns a warning-only run into exit code 2. --enable <RULES> runs exactly the listed rules (comma-separated IDs, or ALL) in place of the config's selection, and needs no config file.
• Pass - as the input to read YAML from stdin (ruff convention). Add --stdin-filename <PATH> so diagnostics, project-config discovery, and path-based filtering (yaml-files, per-file-ignores, per-rule ignore) use that filename. Without it, diagnostics are labelled <stdin>, config is anchored at the current working directory, and all path-based filtering is skipped so every enabled rule runs. - cannot be combined with other inputs; --fix cannot read from stdin, but --diff can.
• ryl server runs ryl as a Language Server (LSP) over stdio, giving editors inline diagnostics, a source.fixAll.ryl code action, and formatting via ryl format. It complements Red Hat's yaml-language-server rather than replacing it, and is built in by default (a minimal binary without it builds with cargo install ryl --no-default-features). See https://ryl-docs.pages.dev/editor-integration/.
• Run ryl --help for the authoritative CLI reference.

For installation walkthroughs, configuration presets, and per-rule documentation, see the docs site.

Performance

The figure below times ryl and yamllint over a 5x5 file-count × file-size matrix with 5 runs per point:

The benchmark script is in scripts/benchmark_perf_vs_yamllint.py; run it with --help for the full option set.

Acknowledgements

This project exists thanks to the tooling and ecosystems around YAML linting and developer automation, especially:

• yamllint - for giving me the shoulders to stand on and the source of many of the automated tests that ryl uses now to check for behaviour parity. Copying the behaviour of an existing tool is infinitely easier than building one from scratch - there'd be no ryl without yamllint.
• ruff - for showing the power of Rust tooling for Python development and inspiring the config and API for ryl.
• rumdl - for giving me another template to follow for Rust tooling.
• saphyr - ryl's vendored YAML DOM is derived from saphyr, and saphyr's developers were very patient in showing some of the nuance and complexity of parsing YAML which I was embarrassingly ignorant of when starting ryl.
• granit-parser - a saphyr-parser fork with comment and style metadata that ryl uses for event-stream parsing.
• esbuild and biome - for providing the "binary wrapper" blueprint for distributing high-performance native tools via NPM.