Regex Tester
Build, test, debug, and replace text with PCRE-compatible regular expressions.
5 matches found.
Matches
HelloOffset 0BuildOffset 27BetterOffset 33DeveloperOffset 40ToolsOffset 50Replacement Preview
[Hello] from SmartToolsNest. [Build] [Better] [Developer] [Tools].
How to Use
Enter a pattern without delimiters, choose flags, paste test text, and inspect every match, offset, capture group, and replacement result.
Supported Flags
- g
- Global
- i
- Ignore case
- m
- Multiline anchors
- s
- Dot matches newline
- u
- Unicode mode
Related Tools
Test expressions before shipping them
Regex behavior depends on flags, anchors, greediness, and capture groups. Validate representative inputs and edge cases before using a pattern in validation or data processing.
Frequently Asked Questions
Which regex flavor is used?+
The tester uses PHP PCRE syntax. Enter the pattern without surrounding delimiters.
How do capture groups work?+
Parenthesized subpatterns appear beneath each full match.
What does global mean?+
Global mode returns every non-overlapping match instead of only the first.
Is catastrophic backtracking possible?+
Poorly designed patterns can be expensive; keep patterns and test data bounded.
Related Articles
Developer newsletter
Stay ahead with new tools
Get practical developer guides, new tools, and workflow improvements without inbox noise.