RedPen is a proofreading tool to help writers or programmers who write technical documents or manuals that need to adhere to a writing standard. It provides both a simple standalone command line tool and a server.
RedPen automates the verification of input documents written in natural languages — NOT computer languages such as C++ or Java.
This is free and open source software.
Key Features
- Supports various input text formats: Plain text, Markdown, Textile, AsciiDoc, Wiki, Re:VIEW, reStructuredText, LaTeX, and Java Properties.
- Output formats supported: Plain text, XML, and JSON.
- Highly customizable. Choose provided validators and add them to your configuration file.
- Works with documents with any languages (English, German, Japanese, Chinese…).
- Server – provides not only a UI but also a practical REST API.
- Plugin system: users can write their extensions with JavaScript.
- Annotation based error suppression.
- Cross-platform support – runs under Linux, macOS, and Windows.
Website: redpen.cc
Support: github.com/redpen-cc/redpen
Developer: Takahiko Ito
License: Apache License 2.0

RedPen is written in Java. Learn Java with our recommended free books and free tutorials.
Related Software
| Linters | |
|---|---|
| LanguageTool | Style and grammar checker for 30+ languages |
| Vale | Write with a consistent tone and style |
| ALE | Asynchronous Lint Engine |
| textlint | Pluggable linting tool for text and markdown |
| Harper | English grammar checker designed to be just right |
| proselint | As the name suggests, this is a linter for prose |
| alex | Catch insensitive, inconsiderate writing |
| write good | Linter for English prose |
| Eloquent | Works fully offline, powered by the LanguageTool standalone server |
| RedPen | Provides both a simple standalone command line tool and a server |
Read our verdict in the software roundup.
Explore our comprehensive directory of recommended free and open source software. Our carefully curated collection spans every major software category.This directory is part of our ongoing series of informative articles for Linux enthusiasts. It features hundreds of detailed reviews, along with open source alternatives to proprietary solutions from major corporations such as Google, Microsoft, Apple, Adobe, IBM, Cisco, Oracle, and Autodesk. You’ll also find interesting projects to try, hardware coverage, free programming books and tutorials, and much more. Discovered a useful open source Linux program that we haven’t covered yet? Let us know by completing this form. |

