Free tool · Dev Utilities
Regex Tester
Test a regular expression against sample text.
Enter a regular expression and a block of test text to see every match listed instantly, along with capture groups. Matching is debounced so it does not re-run on every keystroke, and results are capped at a readable limit so a pattern with thousands of matches stays responsive rather than flooding the page. Useful for building and debugging a regex before dropping it into code, without needing to run a script just to test a pattern.
- Files never leave your device
- Runs entirely in your browser
- Free, no account needed
How to use Regex Tester
Two steps, and nothing to install.
Enter your pattern and test text
Type your regular expression, set any flags you need, and paste in the text to test it against.
Review the matches
Every match and its capture groups appear automatically as you type, updating live.
More free tools
Free, private, and no sign-up on any of them.
How this works in your browser
This tool uses your browser’s native RegExp engine, the same one used in every JavaScript environment, so behavior matches exactly what your own code will do. Matching runs debounced (a brief pause after you stop typing) rather than on every keystroke, and a very large test block is rejected with a clear message rather than silently freezing the tab.
Regex Tester vs. upload-based online tools
| Feature | Regex Tester (in-browser) | Upload-based online tools |
|---|---|---|
| File upload required | No - never leaves your device | Yes - file is sent to a server |
| Processing queue | None - starts instantly | Often, especially at peak times |
| Watermark on output | Never | Common on free plans |
| Usage limits | None - free, unlimited use | Often capped per day or file size |
| Works offline once loaded | Yes, for most tools | No - requires a live connection |
| Account required | No | Often, for anything beyond a trial |
Who uses Regex Tester
Developers writing validation logic
Build and confirm a pattern for form validation, parsing, or a find-and-replace before committing it to code.
Debugging an existing regex
Paste in a pattern that is not matching what you expect and see exactly which parts of your text it does and does not catch.
Learning regular expressions
Experiment with patterns and flags and see the effect immediately, without setting up a script.
Frequently asked questions
What it can and cannot do, and what happens to your files.
Is this regex tester free?
Yes, completely free with no limit on how many patterns you test.
Which regex flavor does this use?
Standard JavaScript regular expression syntax, the same engine used in browsers and Node.js.
Can I see capture groups, not just the full match?
Yes, each match’s capture groups are shown alongside the full match.
Does this support flags like case-insensitive or global?
Yes, common flags (g, i, m, s) can be toggled.
What happens with a very complex pattern or huge test text?
Matching is capped at a readable number of results and test text over a set length is rejected with a message asking you to trim it, so a runaway pattern can not hang your browser tab indefinitely.
Test a regex - free and instant.
Files never leave your device. No upload, no account, and free for unlimited use.