Regex Tester
Regex Tester
Validate regular expressions, extract from logs, write form validation, or run bulk text substitutions β all in your browser. Match positions, capture groups, and replacement output appear in a single view.
Your input is never uploaded. Patterns, text, and replacement output stay inside your browser.
Pattern
Regular expression
/(?<user>[A-Za-z0-9._%+-]+)@(?<domain>[A-Za-z0-9.-]+\.[A-Za-z]{2,})/gmu
Flags
Samples
Text
Test text
Runs entirely in your browser
Patterns, text, and replacement output are processed inside the browser only β nothing is sent to a server.
- No uploads
- No sign-up
- Optional local save
How to
How to use
- 1
Enter a pattern
Type the regex you want to test and toggle the flags you need (g, i, m, β¦).
- 2
Provide text
Paste the text you want to match against, or load one of the sample templates.
- 3
Review matches
Review match count, position, line numbers, and capture groups.
- 4
Replace & save
Optionally enter replacement text, then copy or download the substituted output.
FAQ
Frequently Asked Questions
Is my data sent to a server?
No. Patterns, test text, and replacement output are processed entirely in your browser.
Which regex flavor is supported?
Matching uses your browser's regular-expression support. Lookbehind, lookahead, and named capture groups depend on the browser.
What if matching never finishes?
Matching stops automatically after 3 seconds. Simplify the pattern and try again if it times out.
Are replacement back-references supported?
Yes. $1, $2, $& and $<name> are supported. You can also replace just the currently selected match.
How large a text can I test?
Up to about 1,000,000 characters. Above 100,000 characters auto-run is paused so you can press Run on demand.