- Enter your pattern in the regex field and your test text below it.
- Watch the live results update as you type — every match is listed with its total count.
- Load a preset from the common patterns menu to start from a proven template, then tweak it for your data.
All matching happens locally in your browser. Nothing you type is uploaded, so you can safely test patterns against real log lines, user input and other data that may be private.
A regular expression is a small program, and like any program it needs testing before it can be trusted. Seeing the matches side by side with your text makes the behavior obvious: a pattern that looks right on paper often captures more — or less — than you expect. The match list shows exactly which substrings were found, so edge cases surface immediately instead of failing silently in production code.
Tips
Start with a simple pattern and add pieces step by step; debugging a long regex that fails is much harder than building it up incrementally. Remember that metacharacters such as . and * are greedy by default and match as much as possible, which is a common source of surprising results.
Test edge cases on purpose: an empty string, very long input, and text that contains line breaks. The invalid-regex message also catches typos such as unclosed brackets the moment you type them, so fix the pattern before it reaches your code.
Why use it
Iterating on a regex by editing and re-running code costs minutes per attempt; this tester gives instant feedback in the browser. It is free, needs no installation, and combines live matching with useful presets — everything you need to get a pattern right the first time.
Real-world use cases
- API development: Format JSON responses from Chrome DevTools before committing fixtures.
- Debugging: Validate timestamps, regex or hashes without switching to a terminal or IDE.
- On-call fixes: From your phone, quickly convert timezone or generate a UUID for a hotfix branch.
How it compares
| Tool | Offline | Privacy | Setup | Cost |
|---|---|---|---|---|
| This tool | Yes | 100% local | None | Free |
| Server tools | No | May log IP | None | Free/Ads |
| CLI / IDE plugin | Yes | Local | Install & config | Free |
For quick checks without context switching, the browser tool is fastest. For CI, keep the CLI as source of truth.
Pro tips
- Bookmark the tool. With prefetch enabled, it opens near-instantly next time.
- For secrets like hashes with salts, prefer your local terminal for production values.
- Pair UUID/Password generators with your password manager for rotation workflows.