Vale
Vale is an open-source command-line linter for prose under MIT that turns a team's writing guidelines into automatic checks, running in an editor, in continuous integration and alongside code, entirely offline. It understands document structure in Markdown, AsciiDoc, reStructuredText and HTML, skipping code and URLs, and can check comments inside source files. Rules are YAML files, from banned word lists to readability formulas, and published style guides are available.
What does Vale do?
Vale is "a command-line linter for prose" that turns "your team's writing guidelines into checks that run in your editor, in CI, and alongside your code." Its stance is deliberate: "Vale doesn't ship opinions of its own. It's a framework for enforcing your style", with published guides from Microsoft, Google, Red Hat and others available alongside your own house terms.
It reads structure rather than plain text: "Most tools see text. Vale sees a document." It parses Markdown, AsciiDoc, reStructuredText and HTML, skipping code spans, URLs and code blocks, and can check comments and docstrings inside source files. Views find prose inside API descriptions, notebook cells and commit messages. Rules are YAML, from banned word lists to grammar patterns, readability formulas and scripts, and a rule can carry its own fix. Spell checking is included. It is one Go binary, checks files in parallel, and its README says "Nothing leaves your machine: no account, no upload, and no training on your writing."
Key facts
- Licence: MIT, copyright Joseph Kato, with no added conditions; contributors sign a contributor licence agreement.
- A rule engine, not a model: rules are YAML files, and published style guides from Microsoft, Google and Red Hat are available.
- Understands Markdown, AsciiDoc, reStructuredText and HTML structure, skipping code and URLs; checks comments and docstrings in source files using tree-sitter.
- Views extract prose from API descriptions, notebook cells and commit messages.
- Rules range from banned terms to grammar patterns, readability formulas and scripts, and can include fixes; spell checking is included.
- One Go binary, files checked in parallel; nothing is uploaded, by the README.
- Install: Homebrew, Chocolatey or winget, snap, pacman or apt, Docker, go install, or a prebuilt binary; configure a .vale.ini, run vale sync then vale on a path.
- The README links Vale Studio and Vale CMS for authoring in a browser; whether they are paid is not stated. Latest tagged release when read: v3.22.0 on 2026-09-17; 6,109 stars.
What does it replace, and where does it fall short?
Vale replaces Grammarly for a documentation team that wants its own style guide enforced consistently, in the editor and on every pull request, rather than one company's opinion about good writing. It is the pick for teams and style guides on the open-source alternatives to Grammarly page.
Where it falls short: it enforces the rules you give it, so it needs setting up, and it does not rewrite sentences or check grammar as deeply as a rule engine built for grammar. The README names no specific editors. Its maintainer describes himself as the sole developer. For grammar in many languages, LanguageTool; for AI rewriting, Writing Tools.
How does Vale run?
Install with Homebrew on macOS, Chocolatey or winget on Windows, snap, pacman or apt on Linux, Docker, go install, or a prebuilt binary. Add a .vale.ini configuration, run vale sync to download the styles it names, then vale on a path. It runs the same way in CI, so writing checks fail a build like tests do.
Who is Vale for?
A documentation or content team that wants its own house style checked automatically on every change. An individual who wants general grammar help should use LanguageTool, Harper or Writing Tools.
What limits does the README state?
None stated in the README; its only related note is that it has a sole developer.
Questions people ask
Is Vale open source?
Yes. Vale is MIT licensed with no added conditions, and contributors sign a contributor licence agreement. The README links Vale Studio and Vale CMS for authoring rules in a browser, without saying whether either is paid.
Does Vale check grammar?
It checks what your rules say to check. Rules can cover banned terms, grammar patterns, readability formulas and scripts, and published style guides from Microsoft, Google and Red Hat are available. It also includes spell checking. It has no opinions of its own, by design.
Can Vale run in continuous integration?
Yes. That is one of its three stated homes, alongside your editor and your code. Because it is a single Go binary with a configuration file, a documentation check can fail a pull request the same way a failing test does.
Does Vale send my writing anywhere?
No. The README says nothing leaves your machine: no account, no upload, and no training on your writing. It runs as a local binary, and vale sync downloads only the style packages your configuration names.
How does Vale compare with Grammarly?
Vale enforces your team's own writing guidelines automatically, in editors and CI, offline and free. Grammarly applies its own suggestions and AI rewriting as a hosted service. The open-source alternatives to Grammarly page compares it with LanguageTool, Harper, Writing Tools and LTeX+.
Sources
- Vale README and MIT LICENSE: github.com/vale-cli/vale, read 2026-09-17.
Compared with the others
On the open-source alternatives to Grammarly page, Vale is the pick for a team's own style guide, enforced. MIT prose linter that turns writing guidelines into checks in editors and CI, understanding Markdown, AsciiDoc and code comments, entirely offline.
Also on that page: LanguageTool for grammar in more than 25 languages, Harper for fast english checking in your editor, Writing Tools for ai rewriting anywhere on screen.
More writing and grammar
An Apache-2.0 English grammar checker from Automattic that lints a document in milliseconds, uses a fraction of LanguageTool's memory by its own measure, runs privately in your editor or in the browser through WebAssembly.
An LGPL-2.1 proofreading engine for English, Spanish, French, German, Portuguese, Polish, Dutch and more than 20 other languages, which you can run as your own HTTP server with an API, or inside LibreOffice.
A GPL-3.0 system-wide writing assistant for Windows, Linux and macOS that rewrites, proofreads or summarises selected text anywhere with one hotkey, using a local model through Ollama or a cloud model with your own key.
Added September 17, 2026. Every claim above comes from the project's README, LICENSE or model card, read on September 17, 2026, or from the GitHub API on the date shown in the panel. Found an error? Write to reveneau@licheo.com and it is fixed in the next weekly pass. Repository: github.com/vale-cli/vale.
Running one of these inside your own environment, with your own data and your own security rules, is the kind of work Reveneau does. Read how a forward deployed engagement works.