Debug an extraction pattern
Inspect every match position and capture group against sample text.
Regex Tester with Match and Replace Preview
Regex Tester with Match and Replace Preview
Test JavaScript regular expressions with match positions, capture groups, highlighting, and replacement output.
Key features
- Combines the g, i, m, s, u, and y JavaScript regex flags.
- Lists every match index plus positional and named capture groups.
- Highlights matches in the test text and previews $1 or $<name> replacements.
- Includes quick patterns for email, URLs, numbers, phone numbers, and more.
How to use
- Enter a pattern and choose flags.
- Inspect matches and captures in the test text.
- Open replacement preview when you need to test substitution output.
Examples
Validate a replacement expression
Preview regex replacement output before applying the logic to real data.
Privacy
Regex execution, highlighting, and replacement previews run in your browser; the pattern, flags, and test text are kept in that browser's local storage.
Requirements
Risky patterns are rejected, with limits of 1,000 pattern characters and 100,000 input characters.
Common questions
- Which regex syntax and flags are used?
- It uses JavaScript regular-expression syntax with combinations of g, i, m, s, u, and y flags.
- Can I inspect capture groups and replacements?
- Yes. Numbered and named captures are listed per match, with a preview for $1 or $<name> replacements.
Related tools
- Find and Replace Text OnlineFind literal text or regular-expression matches and replace the first occurrence or every occurrence.
- Line-by-Line Text Difference CheckerCompare original and revised text with an LCS-based line diff in unified or side-by-side views.
- Extract URLs from TextPull HTTP(S) and www addresses from long text, clean duplicates or tracking parameters, and format the link list.
- String Escape and Unescape ConverterEscape newlines, tabs, and quotes, or restore Unicode and hexadecimal escape sequences to literal characters.