RedPen
RedPen is a free, open-source proofreading tool for writers and programmers preparing technical documents or manuals that follow a writing standard.
What RedPen is
RedPen is a free, open-source proofreading tool for writers and programmers preparing technical documents or manuals that follow a writing standard. It checks natural-language text rather than programming languages and supports languages including English, German, Japanese, and Chinese. Validation covers Markdown, Textile, AsciiDoc, reStructuredText, and LaTeX, with users selecting validators through a configuration file. Rules issue warnings for review. RedPen can run from the command line, including in a Travis CI workflow, and provides a REST API and user interface. Integrations and packages cover Atom, Emacs, Vim, WordPress, IntelliJ IDEA, Sublime Text, and Visual Studio Code. Its IntelliJ plugin validates supported text as an editor inspection, while the WordPress plugin checks posts as they are written. JavaScript extensions are supported. The project runs on Linux, macOS, and Windows, and its repository identifies the Apache-2.0 license.
Good
- Free and open source
- Supports multiple markup formats
- Configurable validators and style rules
- Integrations across editors and WordPress
- REST API and JavaScript extensions
Watch out
- Checks natural language, not programming languages
- Rules warn rather than automatically correcting
- Configuration is required for chosen validators
- Platform integrations vary by editor
Who it suits
RedPen suits technical writers and programmers who need configurable style or terminology checks. It is useful when documents move through supported markup formats, editors, command-line workflows, or APIs.
Verdict
RedPen provides configurable proofreading across technical formats and many writing environments. Its warnings, integrations, and API make it adaptable for document standards and terminology control.
The facts
Each one read from RedPen's own pages, with the date it was checked.
What it does
- API and UI
- The project README links to a REST API and user interface.checked 8 Oct 2026
- Audience
- RedPen is described as a tool for writers or programmers producing technical documents or manuals that must follow a writing standard.checked 8 Oct 2026
- Command-line and CI
- A maker blog describes running RedPen from the command line in a Travis CI workflow to check document quality.checked 8 Oct 2026
- Customization
- Users can choose validators and add them to a configuration file.checked 8 Oct 2026
- Document formats
- It validates markup text including Markdown, Textile, AsciiDoc, reStructuredText, and LaTeX.checked 8 Oct 2026
- Extensions
- The project supports a plugin system that lets users write extensions with JavaScript.checked 8 Oct 2026
- External validation
- The WordPress plugin blog says it uses a public RedPen server by default and can be configured to use the user's own RedPen Server instance.checked 8 Oct 2026
- Formats
- The site lists Markdown, Textile, AsciiDoc, reStructuredText, and LaTeX as supported markup formats.checked 8 Oct 2026
- Integrations
- The project lists integrations or packages for Atom, Emacs, Vim, WordPress, IntelliJ IDEA, Sublime Text, and Visual Studio Code.checked 8 Oct 2026
- JetBrains integration
- The RedPen IntelliJ IDEA plugin adds text validation as an editor inspection and supports plain text, properties and resource bundles, Markdown, and AsciiDoc when relevant plugins are installed.checked 8 Oct 2026
- Languages
- The maker says RedPen works with documents in languages including English, German, Japanese, and Chinese.checked 8 Oct 2026
- License
- The project repository identifies its license as Apache-2.0.checked 8 Oct 2026
- Natural-language checking
- It automates checks on documents written in natural languages, rather than programming languages.checked 8 Oct 2026
- Purpose
- RedPen is a proofreading tool for writers and programmers who write technical documents or manuals that must follow a writing standard.checked 8 Oct 2026
- REST API
- The RedPen Server provides REST endpoints for validating documents with preset or user-supplied configuration.checked 8 Oct 2026
- Support
- The maker's site links to a mailing list and chat room for contact and support.checked 8 Oct 2026
- WordPress integration
- The RedPen WordPress plugin validates posts while users type and can highlight errors in the editor.checked 8 Oct 2026
Where it runs
- Platforms
- The project README lists macOS, Windows, and Linux as supported platforms.checked 8 Oct 2026
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