Comby
Comby is a free, open-source tool for searching and changing code structure with lightweight templates.
What Comby is
Comby is a free, open-source tool for searching and changing code structure with lightweight templates. It recognizes basic syntax in code, strings, and comments across many languages, with basic parsers for C/C++, C#, Go, Java, JavaScript, Python, Rust, Swift, and TypeScript, plus a generic matcher for other formats. It matches balanced delimiters while accounting for comments and string literals, and is suited to coarse syntactic matching, large refactors, and one-off changes. An interactive review mode lets users inspect proposed edits. Comby can be used from the command line, through Python bindings, or with HTTP requests to a server on the user's machine. Installation instructions cover macOS, Ubuntu, Windows through Ubuntu on WSL, and Docker; building from source is also described. The project links to an Emacs package and a prototype VS Code extension. Its API documentation notes that rewrite ranges currently report line and column as -1, and repeated hole identifiers in a rewrite template return only the first range. Comby does not treat indentation as significant, limiting its use with indentation-sensitive structures such as Python blocks.
Good
- Matches balanced delimiters while accounting for comments and strings.
- Interactive review lets users inspect proposed edits.
- Usable through CLI, Python bindings, or HTTP requests.
- Supports basic parsers for many languages.
- Open-source Apache-2.0 license.
Watch out
- Does not treat indentation as significant.
- Rewrite range line and column values are -1.
- Repeated rewrite holes report only the first range.
- Not suited to formatting changes such as line wrapping.
Who it suits
Comby suits developers making structural code searches or coarse refactors across supported languages. It may also suit people exploring uses such as compiler fuzzing, test case reduction, editor find and replace, or academic research.
Verdict
Comby provides structural matching and rewriting with several ways to integrate it into a workflow. Its indentation and API range limitations matter for certain edits, so check that they fit the task before relying on it.
The facts
Each one read from Comby's own pages, with the date it was checked.
What it does
- API limitation
- The API documentation says rewrite ranges currently report line and column as -1, and repeated hole identifiers in a rewrite template currently report only the first range.checked 4 Oct 2026
- Best-fit work
- Comby is suited to coarse syntactic matching and refactoring, while the FAQ says it is not well-suited to styling or formatting changes such as inserting line breaks at a set width.checked 8 Oct 2026
- Editor integrations
- The projects page links to an Emacs package and a prototype VS Code extension.checked 4 Oct 2026
- Installation
- The getting-started page documents installation on macOS with Homebrew, Ubuntu with a shell installer, Windows through Ubuntu on WSL, and Docker.checked 8 Oct 2026
- Install options
- The site provides installation instructions for macOS, Ubuntu, Windows through Ubuntu on WSL, and Docker, and also describes building from source.checked 4 Oct 2026
- Integration
- Comby can be used through Python bindings, its command line, or HTTP requests to a server run on the user's machine.checked 4 Oct 2026
- Integration options
- Comby provides an API reference for building or integrating other tools, and the projects page lists an Emacs package and a prototype VS Code extension.checked 8 Oct 2026
- Interactive review
- Comby supports an interactive review mode for proposed changes.checked 4 Oct 2026
- Language awareness
- Comby understands basic syntax for code, strings, and comments in many languages.checked 8 Oct 2026
- Language coverage
- Comby lists basic parsers for languages including C/C++, Go, JavaScript, Python, Rust, and TypeScript, with a generic matcher for other formats.checked 4 Oct 2026
- Language support
- Comby has basic parsers for languages including C/C++, C#, Go, Java, JavaScript, Python, Rust, Swift, and TypeScript, plus a generic matcher for other formats and languages.checked 8 Oct 2026
- License
- The public comby-tools/comby GitHub repository identifies its license as Apache-2.0.checked 8 Oct 2026
- Notable limitation
- Comby does not currently treat indentation as significant, which limits support for matching indentation-sensitive structures such as Python blocks.checked 8 Oct 2026
- Purpose
- Comby is a tool for searching and changing code structure using lightweight templates.checked 8 Oct 2026
- Refactoring
- The site describes Comby as useful for large scale refactoring and one off code changes.checked 4 Oct 2026
- Rewrite helpers
- Built-in rewrite properties can change letter case and provide match lengths, positions, and file context.checked 8 Oct 2026
- Security and compliance
- The opened product and documentation pages do not state security certifications or compliance claims.checked 4 Oct 2026
- Self hosting
- The project can be built from source, and the getting-started page describes building it for other platforms or local development.checked 8 Oct 2026
- Structural matching
- Comby matches balanced delimiters such as parentheses, brackets, and braces while accounting for comments and string literals.checked 8 Oct 2026
- Support
- The help page directs users to the Gitter channel for usage questions and pattern-writing help, and to GitHub issues for installation problems.checked 8 Oct 2026
- Use cases
- Documented uses include large-scale refactoring, structural code search, fuzzing, editor find-and-replace, and academic research.checked 8 Oct 2026
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