regex101 is a browser-based tool for building, testing and debugging regular expressions. Its editor supports PCRE2, JavaScript, Python, Golang, Java, .NET 10.0, Rust, POSIX ERE, POSIX BRE and legacy PCRE. Explanations show how each part of a pattern matches under the selected flavor, and a step-through debugger helps inspect matching. Results can be exported as JSON, JSON Lines, CSV or plain text. Developer integrations include HTTP APIs, an MCP server, editor links and a separately licensed parser package. The workspace API stores editor data but does not provide a remote matching endpoint. File loaders process text, bytes and supported documents locally in the browser; saving or sharing workspace input can send it to the workspace service. The free plan includes core regex tools, one test string and saved workspaces with an account. Pro costs 4.99 EUR per month, billed yearly, and adds multiple test strings, substitution pipelines, advanced benchmarking, formatting and an ad-free workspace. A self-hosted Enterprise option is listed with annual invoice billing; its standard deployment uses Linux, Docker Compose, MySQL and Redis.
Who it is for
regex101 suits developers and others who need to build or inspect regular expressions across multiple language flavors. Its API, editor links and self-hosted Enterprise option may also suit teams with integration or deployment requirements.
What is good
- Supports ten listed regex flavors.
- Explains pattern matching according to the selected flavor.
- Exports results as JSON, JSON Lines, CSV or text.
- Free plan includes core tools and saved workspaces.
- Self-hosted Enterprise deployment is documented.
What to know first
- Free plan allows one test string.
- Workspace API does not offer remote matching.
- Saving or sharing workspace input can send it to the service.
- Pro is 4.99 EUR per month, billed yearly.
Verdict
regex101 combines multi-flavor pattern testing with explanations, debugging and export options. The free plan is limited to one test string, while Pro adds larger workflows at the listed yearly-billed monthly rate.
regex101 plans and pricing
All plansCompared on regular expression testers
- Free plan
- Yes
- Regex flavors
- PCRE2 (PHP), JavaScript, Python, Golang, Java, .NET, Rust, POSIX ERE, POSIX BRE, PCRE (Legacy)
- Pattern explanation
- Yes
- Step-through debugger
- Yes
- Code generation
- Yes
- Saved patterns
- Yes
