100% local processing — your files and data never leave this browser. No uploads, no server storage.
Free · Browser-only · No upload
Use this regex tester online to test regular expression patterns against sample text. Whether you need a quick regex test, an online regex tool for debugging, or an online regular expression tester while building forms and parsers — results stay on your device.
A regex checker online lets you iterate on patterns without writing a throwaway script. Paste a candidate expression, toggle flags, and read match indices and capture groups. It is the same loop you would run in DevTools, packaged as a dedicated regex expression tester for sharing with teammates.
Search terms like regex builder online, regex generator online, and regex creator online often mean the same outcome: confirm a pattern before shipping it — which is what a regular tester is for.
Start with a literal substring, add escapes, then boundaries (^ $), then grouping. Use g when you need every occurrence. The online regular expression builder mindset is: small samples, explicit flags, inspect groups — repeat until the match list looks right.
Logs, payloads, and customer emails stay in your browser. For compliance-sensitive workflows, that makes this regex evaluator safer than pasting into unknown third-party APIs.
Common questions
Flags, match groups, and how this differs from server-side regex engines.
This is a JavaScript RegExp engine (ECMAScript). Most syntax matches PCRE, but features like lookbehind support depend on your browser version. For PHP or Python-specific assertions, validate in those runtimes too.
Check flags: without g you only get the first match; with ^/$ and m, anchors behave per line. Also confirm you are not accidentally including trailing newlines in the test string.
Parentheses in your pattern create groups. Group 1 is the first (...), group 2 the second, and so on. Non-capturing (?:...) groups are excluded from the groups list.
Pathological patterns on long strings can be slow (catastrophic backtracking). Test with shorter samples first. This tool runs synchronously in-tab — very large inputs may stutter.
No. Patterns and sample text stay in memory in your browser until you close or refresh the page.
Generators propose patterns from examples. This page is a regex evaluator / checker: you write or paste a pattern, set flags, and inspect matches — closer to an online regular expression builder for iteration.