Regex Tester
Test regex against samples live.
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Heavy libraries load on demand so the page shell stays fast.
About Regex Tester
Regex Tester lets you write and debug regular expressions against sample text live in the browser — capture groups, flags, and match highlighting without pasting production logs into a random online playground that stores history.
How to use Regex Tester
- 1Paste sample text you own or have sanitized.
- 2Enter the pattern and flags.
- 3Inspect matches and groups as you edit.
- 4Copy the final pattern into your codebase or editor.
Frequently asked questions
Which regex flavor?
Behavior follows JavaScript’s RegExp engine in your browser. Some .NET/Java features differ.
Catastrophic backtracking?
Pathological patterns can freeze the tab. Start simple and test on small samples first.
PII in samples?
Sanitize before pasting. Even local tools can leak via screen shares or synced clipboard managers.
Replace mode?
Use match testing to validate, then apply replacements in your editor or script with the same pattern.
Learn regex here?
The tester is a workbench. Pair with docs or tutorials for syntax; Toolncy focuses on private iteration.