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Codebase intelligence for TypeScript and JavaScript.

Health, complexity, duplication, architecture, styling and unused code, from one graph of your repository. Fallow is free and open source, and it is built for people, CI and the coding agents that write your code.

Read the quickstartView on GitHub

Run it in a project now:

npx fallow
  • MIT license
  • Runs on your machine
  • No account
site/featuresdashboard/componentssrc/servicesdashboard/publicdesign-systemsite/scriptssrc/libdashboard/libdashboard/routessite/workersrc/routes

Findings from all lenses: 142 of 545 files. A real fallow viz scan of the fallow.cloud codebase.

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3.82M
Teams at these companies use Fallow in their public repositories.

One graph, many views of your code.

Fallow builds one graph of the whole repository, with workspaces, re-exports and framework conventions. Each analysis reads that graph, so the results agree with each other.

  • Health and complexity

    A health score per file, and the functions that are hard to read and change, ranked with churn so you know where to start.

    How it works

  • Duplication

    Repeated code across files, also when names and literals differ, so you can merge it into one place.

    How it works

  • Architecture

    Circular dependencies and imports that cross the boundaries you define between layers and packages.

    How it works

  • Styling

    Values that bypass your design tokens, repeated blocks, complex selectors and broken references in the styles you ship.

    How it works

  • Changed code

    A check of a branch or a pull request that reports only the problems the change adds, with the risk of each file.

    How it works

  • Unused code

    Unused files, exports, types and dependencies, with a dry run before any automatic fix.

    How it works

Use it where you already work.

One analysis engine serves every surface, so the terminal, the pull request and the editor agree.

Terminal
Run npx fallow in any project. Human output by default, JSON for scripts.
QuickstartInstallation
CI
The GitHub Action and the GitLab CI template comment on a pull request and fail on new problems only.
CI integration
Editor
The VS Code extension and the language server show each finding where you write the code.
VS CodeNeovim
Coding agents
The MCP server and the agent plugins give Codex, Claude Code and other agents the same facts.
MCP serverAgent plugins

Built in the open.

Fallow is an open-source project. The code, the issues, the roadmap discussions and the releases are public.

Source code
The analyzer, the CLI, the language server, the MCP server and the editor extension are MIT licensed.
fallow-rs/fallow on GitHub
Contribute
Report a false positive, add a framework plugin or fix a bug. The contributing guide explains the setup.
Contributing guide
Ask and discuss
Ask a question, share a result or propose a feature in GitHub Discussions.
GitHub Discussions
Security
Report a vulnerability in private. The security policy gives the process and the response times.
Security policy
Sponsor
Sponsorship pays for maintenance time, releases and the free public infrastructure of the project.
GitHub Sponsors
Releases
Each release lists what changed, with a link to each pull request.
Changelog

Run it on your project.

Start in the root of a repository. Fallow finds the entry points from your package.json and your framework configuration, so the first run needs no configuration.

Read the quickstartnpx fallow