Regex Tester
Text /regexTest ECMAScript regular expressions locally with flags, match results, capture groups, and replace preview.
Results update as you edit the pattern, flags, and text.
<JSON> formatter <json> validator
Match 1 · 0-4 JSON Groups: JSON Match 2 · 15-19 json Groups: json
2 matches found. 2 lines 29 B local only
How it works
Test ECMAScript regex patterns with flags, capture groups, and replace preview.
Use it to test an ECMAScript pattern against sample text before adding it to code.
Example
Test (json) with gi flags against two lines and inspect both matches and replacement output.
Notes
- This tool uses standard JavaScript RegExp behavior.
- Replace preview follows normal JS replacement semantics.
- Invalid patterns fail inline without changing your source text.
Constraints
- Uses ECMAScript RegExp syntax and runs synchronously in the current browser tab.
- Limit: 1 MiB test text. Nothing is uploaded or silently truncated.
Common errors
- Unclosed groups or classes
- Duplicate flags
- Unexpected global-match behavior
When to use it
Use it to test an ECMAScript pattern against sample text before adding it to code.
Formats: ECMAScript pattern, JavaScript flags, Replacement string.