Regex tester & explainer
Regex Tester and Explanation Tool
JavaScript regular expressions only. Everything runs locally in your browser.
0 matches Valid regex
PatternNo slashes needed (enter the pattern only)
Performance (estimate)
—Run time
—
Text
106 chars
Matches
0
Flags
giu
Enter a valid pattern and some text to measure.
FlagsToggle options
Active: giu
Tip: use g to see all matches; remove it to see just the first.
Test textPaste data or type freely
Highlighted matchesVisual preview
Contact: hello@example.com
Support: support@stackatlas.dev
Invalid: not-an-email@
Upper: Admin@Example.COM
MatchesIncludes capture groups
No matches found.
Max 500 matches rendered to keep things fast.
Regex explanationHuman-readable breakdown
Finds all matches. Looks for a match inside the input using JavaScript regex.
gGlobaliIgnore caseuUnicode
Breakdown
(?<user>
Named capturing group “user”.
[a-z0-9._%+-]
Character class (match one char from the set).
+
Repeat 1 or more times.
)
End of group.
@
Literal character.
(?<domain>
Named capturing group “domain”.
[a-z0-9.-]
Character class (match one char from the set).
+
Repeat 1 or more times.
\.
Escaped literal “.”.
[a-z]
Character class (match one char from the set).
{2,}
Exactly 2 times.
)
End of group.
Quick tips
- Use ^ and $ to validate the whole string.
- Turn on g to see every match in the text.
- Prefer [\\s\\S] if you need “any character” without relying on dotAll.
Common recipes
- \\d+ — one or more digits
- \\b\\w+\\b — whole words
- ^\\S+$ — non-empty, no spaces
- ^(a+)+$ — slow example (backtracking)
Privacy & engine
This tool runs entirely in your browser using the JavaScript regex engine. Your text and patterns are not sent to a server.
If you’re comparing against PCRE/.NET/RE2, behavior can differ (especially around lookbehinds, Unicode, and backtracking).