RegexRegex
RegexRegex is a free browser-based tool for composing and checking regular expressions, with JavaScript as its main locally run engine.
What RegexRegex is
RegexRegex is a free browser-based tool for composing and checking regular expressions, with JavaScript as its main locally run engine. It displays matches, captures, pattern explanations, and errors, and previews replacements using numbered or named capture references. A guided builder helps assemble basic JavaScript patterns from controls for character types, quantities, groups, boundaries, and flags, though it does not cover every syntax feature or turn arbitrary patterns into an equivalent visual layout. The searchable cheat sheet covers 25 syntax and flag items. Test cases can be saved in the browser, up to 50, with each input limited to 20,000 characters. Optional Python, PHP, Java, .NET, and Perl checks run through an online service after the user presses Run; the maker says this service does not record or persist submitted input. Share links omit test and replacement text unless the user opts in. A cached JavaScript checker may work offline, but the other engines require the online service.
Good
- JavaScript checks run locally in the browser
- Shows matches, captures, explanations, and errors
- Previews numbered and named capture replacements
- Saves up to 50 browser-based test cases
- Free online regex tester
Watch out
- Builder covers only basic JavaScript patterns
- Native engine checks require the online service
- Each test input is limited to 20,000 characters
- Offline use may be limited to cached JavaScript checks
Who it suits
It suits developers and learners who need to inspect JavaScript regular expressions, or run optional checks with other listed engines. It may also help users who want a guided builder and browser-saved test cases.
Verdict
RegexRegex provides local JavaScript testing alongside optional online runs for five other engines. Its builder and saved test cases are useful within the stated feature and input limits.
Plans and prices
From RegexRegex's own pricing page, checked 5 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Free online regex tester | Free | JavaScript checks run in the browser · Python, PHP, Java, .NET, and Perl checks require an explicit online run |
The facts
Each one read from RegexRegex's own pages, with the date it was checked.
What it does
- Analytics
- Cloudflare Web Analytics may collect page and device information, and Google Analytics 4 may use analytics cookies if enabled.checked 5 Oct 2026
- Builder
- A guided builder creates basic JavaScript RegExp patterns from controls for character types, quantities, groups, boundaries, and flags.checked 5 Oct 2026
- Cheat sheet
- The checker includes a searchable cheat sheet with 25 regex syntax and flag items.checked 4 Oct 2026
- Data handling
- The execution service does not record or persist input submitted for optional native engine runs.checked 5 Oct 2026
- Engines
- JavaScript runs locally; optional Python, PHP, Java, .NET, and Perl runtimes can be used after explicitly pressing Run.checked 5 Oct 2026
- Integrations
- The opened maker pages describe no external integrations.checked 4 Oct 2026
- Language snippets
- Python and PHP reference snippets are provided, but only JavaScript RegExp executes unless a native engine is explicitly run.checked 5 Oct 2026
- Limits
- The maker says patterns are practical starting points and do not guarantee complete validation for every application.checked 5 Oct 2026
- Local test cases
- Saved test cases stay in the browser, with a maximum input length of 20,000 characters and up to 50 cases.checked 5 Oct 2026
- Offline
- A cached JavaScript checker may work offline, while Python, PHP, Java, .NET, and Perl checks require the online execution service.checked 5 Oct 2026
- Offline use
- A cached JavaScript checker may work offline, while native engine checks require the online execution service.checked 4 Oct 2026
- Privacy
- The privacy policy says the native execution service does not record or persist input submitted for native runs.checked 4 Oct 2026
- Purpose
- RegexRegex is a browser based tool for testing JavaScript regular expressions and inspecting matches, captures, replacement previews, and errors.checked 5 Oct 2026
- Regex builder
- The builder lets users compose basic JavaScript patterns from guided controls and inspect and test the generated pattern.checked 4 Oct 2026
- Regex features
- The checker supports testing matches and captures, previewing replacements, and viewing pattern explanations and errors.checked 5 Oct 2026
- Replacement
- The tester previews replacements and supports numbered and named capture references such as $1 and $<name>.checked 4 Oct 2026
- Share links
- Share links restore selected fields; test and replacement text are excluded unless the user explicitly opts to include them.checked 5 Oct 2026
- Support
- Questions and corrections can be sent to [email protected].checked 5 Oct 2026
- Supported engines
- The checker supports JavaScript locally and offers Python, PHP, Java, .NET, and Perl runtimes when available after the user explicitly presses Run.checked 4 Oct 2026
Money
- Free access
- The maker describes the online regex tester as free.checked 4 Oct 2026
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