Overview

Rather than matching source text alone, ast-grep compares patterns with syntax-tree nodes. That lets a rule target code by structure, which is useful when formatting varies or a text match would catch unrelated code. The CLI can preview and apply rewrites interactively, and the project describes parallel Rust processing for searches and replacements across thousands of source files.

The tool is self-hosted and free, with a CLI, editor support, APIs, and a browser playground. That makes it a practical option for teams that want code search and transformations close to their repositories without adopting a hosted service. The limitation is scope: the FAQ says some advanced static-analysis information is not supported.

Key features

Search, rewrite, and lint

The scan command runs configurable AST-pattern rules with severities including error, warning, info, and hint. This gives teams a way to make structural checks part of a codebase’s linting workflow. The interactive rewrite mode is valuable for broad refactors where users want to inspect matches before applying changes; it does not address checks that require analysis beyond syntax structure.

Rules, languages, and testing

Rules are written in YAML and can combine pattern, kind, regex, relational, and composite matching. CLI commands help create and test rules, including snapshot-based tests, which can make rule changes easier to validate. The project says it supports more than 20 languages and can load custom languages. However, one rule cannot target multiple languages at once. Teams working across languages need a superset language with languageGlobs or separate rules, adding upkeep to shared rule sets.

APIs and integrations

The JavaScript API supports programmatic inspection and changes to syntax trees, while the WebAssembly API extends that access to browsers and other WASM environments. The online playground lets users try patterns and rewrite rules without a local installation. Editor options include an official VS Code extension and language-server support, with documented setups for Vim, Neovim, and Emacs and community integrations for other editors. The language server publishes diagnostics and supports diagnostic code actions; lint diagnostics require an sgconfig.yml project file.

The CLI is distributed through npm, Cargo, Homebrew, MacPorts, Nix, and pip, with source builds also available. That range helps teams fit installation into different environments. The example catalog includes security-oriented rules, such as checks for a Go JSON tag vulnerability and C/C++ format-string risks, but these examples do not make ast-grep a full security-analysis suite.

Pricing

ast-grep is open source and free. Its free plan costs 0.00 USD per free, with no free trial. Because it is self-hosted, teams run it alongside their own code rather than choosing a paid hosted tier. This suits individual developers and organizations that can manage their own tooling; no separate paid plan is needed to access its core search, lint, and rewrite capabilities.

Platforms

ast-grep is listed for API, extension, Linux, macOS, web, and Windows. Its CLI installation options and source builds support a range of developer environments, while the browser playground and APIs cover use beyond the command line. Codebase indexing, regex search, code navigation, and IDE extensions are supported.

Who it's for

Choose ast-grep if your team needs structural code search, custom lint rules, or repeatable refactors across repositories, and values a free tool that can run within its existing development setup. It is particularly useful when rules need to be tested and reused, or when scripts need direct access to syntax trees through JavaScript or WebAssembly.

Look elsewhere or pair it with another tool if your decisions depend on advanced static analysis. Teams maintaining rules across several languages should also account for the one-language-per-rule restriction.

Pros and cons

Pros: Structural matching targets syntax rather than raw text, making searches and rewrites more precise for code-shaped changes.
Pros: YAML rules, severity levels, and snapshot-based rule tests support reusable linting workflows.
Pros: Free, open-source distribution, APIs, editor integrations, and multiple installation routes give teams flexibility in how they adopt it.
Cons: A rule cannot cover multiple languages at once, so polyglot teams may need separate rules or language-specific configuration.
Cons: Unsupported advanced static-analysis information limits its suitability for checks that require deeper program analysis.

Alternatives

Sourcebot is a freemium code-search option with API, self-hosted, and web platforms, and a free plan and trial; consider it when those deployment choices fit better than ast-grep’s structural search and rewriting focus.

Code Search offers a free Community plan with unlimited users, full-text search, repository-wide find and replace, a CLI, and an MCP server. Choose it when full-text search and those collaboration or integration features matter more than AST-based rules.

searchcode is a free tool with API, self-hosted, and web platforms; it may suit readers seeking another free code-search option.

Shebe is a free, locally oriented code-search tool for Linux, macOS, and Windows, and may suit readers looking for that focus.

Hound is another free code-search option, available for API, Linux, macOS, self-hosted, and web use.

Understand is freemium, with a free trial and an annual subscription plan priced at 100120.00 USD per year, billed annually with a 12-month minimum term. Consider it if that subscription model fits your requirements better.

Comby is a free alternative for API, Linux, macOS, self-hosted, and Windows platforms.

LeIndex is a free alternative available for API, Linux, macOS, self-hosted, web, and Windows platforms.

See also the Code Search Tools and Code Refactoring Tools directories.

Verdict

Choose ast-grep if you want free, self-hosted structural search, configurable linting, and code rewriting that fits into a developer workflow. Its syntax-aware rules and broad editor and API options are strong reasons to adopt it; look elsewhere or add another tool when advanced static analysis is central, or plan for extra rule maintenance across languages.

	ast-grep	Kythe
Free plan	Yes	No
Free trial	No	No
Paid from	Free	—
Open source	No	No
Platforms	api, extension, Linux, macOS, Web, Windows	api, Linux, macOS, self-hosted
Indexing scope	codebase	codebase
Deployment	self_hosted	self_hosted
Regex search	Yes	—
Code navigation	Yes	Yes
IDE extensions	Yes	—

ast-grep vs Kythe

ast-grep

Kythe