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Regex Test

Regular expression real-time matching test

e.g. (?<name>\w+)
Flags
Test Text
Enter or paste text to match here...
Matches
Enter a regular expression to see matches
Replacement
Optional, e.g. $2, $1, or $<name>
Replacement Preview
Optional, e.g. $2, $1, or $<name>

togotools.top technical reference

Technical reference

Test regular expressions locally in your browser with real-time match results, capture groups, and replacement preview. Supports global, case-insensitive, multiline, and other flags.

Flags and syntax

g (global)Match all results, not just the first
i (ignore case)Case-insensitive matching
m (multiline)^ and $ match start and end of each line
s (dotAll)Allows . to match newlines
u (Unicode)Correct Unicode code point and astral character handling

Example: extract key-value pairs

Capture groups are referenced as $1, $2 in the replacement field. Named captures (?<key>...) can be referenced as $<key> in supporting engines.

regex
Pattern: (\w+):(\w+)
Input: name:ada age:30 city:berlin
Matches:
  name:ada    -> $1=name $2=ada
  age:30      -> $1=age $2=30
  city:berlin -> $1=city $2=berlin

Limits

  • This tool uses the JavaScript regex engine. Some syntax (lookbehind, atomic groups) differs from PCRE, Python, or Java.
  • Very large input text (over 1MB) may slow matching or freeze the browser.
  • Catastrophic backtracking (ReDoS) can occur with nested quantifiers. Avoid patterns like (a+)+.

Frequently asked questions

Why does my regex work in Python but not here?

JavaScript regex does not support some PCRE features like lookbehind (?<=...) or (?P<name>...) syntax (JS uses (?<name>...)). Adjust the syntax for JavaScript.

Does it support Unicode property escapes?

Yes. With the u flag, you can use property escapes like \p{Letter} and \p{Number}. Requires a modern browser (ES2018+).