# regex101

> regex101 is an interactive regular expression editor, tester, debugger, and sharing service with an OpenAPI-documented HTTP API.

Use regex101 to build, test, explain, debug, benchmark, and share regular expressions. The editor supports PCRE2, PCRE, JavaScript, Python, Go, Java, .NET, Rust, POSIX ERE, and POSIX BRE. It also supports substitution, extraction, unit tests, code generation, regex formatting, ReDoS analysis, saved workspaces, a community library, and a regex quiz.

Most matching and substitution work runs in the interactive application. The HTTP API primarily manages saved workspaces, accounts, library entries, quizzes, and ReDoS analysis. Do not assume that every editor operation has a server API endpoint. Treat the live OpenAPI document as the authoritative API contract.

Use the remote MCP server at `https://regex101.com/mcp`. It provides tools to get, save, update, delete, title, tag, and explain regex workspaces. The MCP client handles OAuth 2.1 browser sign-in with any configured provider. Google, GitHub, and a custom OIDC provider are supported. `GET /connect/providers` lists the providers that are configured for this deployment. Tokens stay outside the model context.

Browser requests use the secure session cookie by default. MCP clients use the OAuth authorization-code flow with PKCE and store the returned session credential outside the model context. The token response includes `expires_in`, which reflects the configured sliding session lifetime. Direct API requests can send this credential as `Authorization: Bearer <token>` and do not need a Cookie header. Signing out invalidates the shared session. Never put bearer tokens in URLs or logs.

## API

- [MCP server](https://regex101.com/mcp): Remote, authenticated tools for regex101 workspace and explanation operations.
- [OpenAPI 3.1 document](https://regex101.com/api/docs/json): Machine-readable paths, request schemas, and response schemas for the deployed API.
- [Interactive API reference](https://regex101.com/api/docs): Swagger UI for exploring the deployed API.
- [API guide and examples](https://docs.regex101.com/application/api/): Authentication and representative workspace requests in cURL, Node.js, and Python.
- [Pro regex explanation](https://regex101.com/api/docs#/explanation/explainRegex): `POST /api/explain` returns a text or structured explanation for a regex when the signed-in account has access.

## Application

- [regex101 editor](https://regex101.com/): Build, test, explain, debug, benchmark, and generate code for regular expressions.
- [Flavor guide](https://regex101.com/static/assets/flavors.md): Markdown guide to supported regular expression engines and language mappings.
- [Community library](https://regex101.com/library): Search and share reusable regular expressions.
- [Regex quiz](https://regex101.com/quiz): Practice regular expression problems.

## Documentation

- [regex101 documentation](https://docs.regex101.com/): Product behavior, API access, Pro features, and frequently asked questions.
- [Regex parser documentation](https://docs.regex101.com/regex-parser/): TypeScript parser capabilities, setup, API concepts, and limitations.
- [Enterprise documentation](https://docs.regex101.com/enterprise/licenses/): Self-hosted licensing and deployment information.

## Optional

- [GitHub project](https://github.com/firasdib/Regex101): Issue tracker and public project files.