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Regex Tester

Test JavaScript regular expressions with live matches and capture groups.

Local processingYour input stays hereSimple controls

Regular expression

Test text

0 characters · 0 bytes

Matches

Enter a pattern and test text to see highlighted matches.

Replace mode

Pattern and flag reference

. matches a character · ^ start · $ end · [abc] character set · ( ) capture group · * zero or more · + one or more · ? optional · {n} repetition.

g finds all matches; i ignores case; m enables line anchors; s lets . match newlines; u enables Unicode; y requires a match at the current position. JavaScript regular expressions are used. Empty matches are marked ∅.

Regex runs in an isolated worker with a 1-second limit. Nested repetition can be very expensive; simplify the pattern if it times out. Maximum 100,000 test characters.

Processed locally in your browser

Your input does not need to be uploaded to an EvryNest server. Nothing is saved automatically.

How It Works

1
Build a pattern
Enter a JavaScript regex or choose a common example.
2
Add test text
Select flags and watch matching text highlighted live.
3
Inspect or replace
Review capture groups or preview replacement text.

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Frequently Asked Questions

How does Regex Tester work?

Patterns run in a worker with a one-second timeout. g, i, m, s, u and y flags use JavaScript semantics.

Does this tool upload or save my input?

Core processing happens locally in this browser tab. Input and output are not sent to a processing server or stored automatically. Copy and download only occur when you request them.

What happens with large or invalid inputs?

Test text is limited to 100,000 characters, patterns to 2,000 characters and processing to one second. Displayed matches are capped at 1,000.