regex101 is an online 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 according to the selected flavor, and users can step through matching. Results can be exported as JSON, JSON Lines, CSV, or plain text. Developer options 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 in the browser; saving or sharing workspace input can send it to the workspace service. The Free plan includes core 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, benchmarking, formatting, and an ad-free workspace. A self-hosted Enterprise option is also listed.
Who it is for
It suits developers and others who need to build, inspect, and debug regular expressions across several syntax flavors. The editor and export options can also help people who need to step through matches or use results in other tools.
What is good
- Supports ten listed regex flavors.
- Explains pattern matching by selected flavor.
- Match results export to four formats.
- Includes step-through matching and code generation.
- Free plan includes saved workspaces with an account.
What to know first
- Free plan includes one test string.
- Workspace API has no remote matching endpoint.
- Pro is 4.99 EUR per month, billed yearly.
- Enterprise support response target is not a guaranteed SLA.
Verdict
regex101 combines a multi-flavor editor, explanations, debugging, and export options. Its Free plan is limited to one test string, while Pro adds more workspace capabilities at 4.99 EUR per month, billed yearly.
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
