Developer / Debugging
Regex Tester
Test regular expressions instantly with live match feedback and editable text input. Test patterns, toggle flags, inspect capture groups, preview replacements, and see matches highlighted in real time.
3
Matches
gm
Flags
26
Pattern chars
Valid
Regex state
Loaded sample regex
Highlighted matches
Replacement result
Match details
Why this one is useful
Seeing matches highlighted in context is much faster than guessing whether a pattern worked from a single true or false.
Replacement preview makes the tool useful for cleanup and transformation tasks, not just validation.
Capture groups, named groups, and flag toggles keep the feedback loop tight, which is the whole point of a good regex tool.
Common uses
Validating IDs, routes, and filename patterns.
Extracting values from logs, copied responses, or pasted text.
Testing multiline and case-insensitive search rules.
Previewing text replacements before writing application code.
Check captures before replacing text
Write a pattern, paste representative lines, then inspect matches and capture groups. Test both a case that should match and one that should not before using the pattern in code.
Named capture example
Use (?<area>\d{3})-(?<number>\d{4}) against 555-0123 to separate the area and number portions. Try 55-0123 as a negative case; add anchors if the whole input must match.
Flags change the result
Global, multiline, and case-insensitive flags do different things. A pattern that works on one sample line can match unexpectedly across a whole document.