Regular expressions are powerful but easy to get subtly wrong, and a regex that looks right can quietly match the wrong things. The fix is to stop guessing and test it against real text as you build it.
Test it live
- Open Regex Tester and enter your pattern and flags.
- Paste the text you want to match against.
- Every match is highlighted as you type, so you see instantly what your pattern catches — and what it misses.
It uses JavaScript's regex engine and runs in your browser, so your test text stays private.
A few tips that save time
- Build up gradually. Start with the simplest pattern that matches one case, then extend it.
- Watch for greedy quantifiers:
.*grabs as much as possible. Use.*?when you want the shortest match. - Remember to escape special characters like
.,(and?when you mean them literally. - Use the case-insensitive flag rather than writing
[Aa]everywhere.
When regex isn't the answer
If you just need to swap one fixed word for another, Find and Replace is simpler and safer than a regex. Reach for regex when the pattern really varies.