New Tool: Regex Tester
Stop Guessing What Your Pattern Matches
Regular expressions are everywhere — validation, search-and-replace, log parsing — yet a single stray character can quietly break a pattern or match far more than you intended. The new Regex Tester gives you immediate, visual feedback: type a pattern, and every match lights up in your test string as you go.
Live Highlighting as You Type
Enter your expression and some sample text, and matches are highlighted instantly. Consecutive matches alternate colors so they are easy to tell apart, and hovering a match in the results list highlights the corresponding span in the text (and vice versa). Even zero-width matches get a visible marker, so you can spot where an empty match lands.
Flags at a Glance
Toggle the standard JavaScript flags with a single click and watch the results update:
- g — global, find all matches instead of just the first
- i — ignore case
- m — multiline, so
^and$match at line breaks - s — dot-all, so
.matches newlines - u — unicode
- y — sticky, match only from the last index
The active pattern is always shown in familiar /pattern/flags form.
Capture Groups, Spelled Out
Every match is listed with its exact character offsets and a breakdown of its capture groups — both numbered ($1, $2) and named ((?<year>…)). Unmatched optional groups are clearly labeled, so you never have to wonder whether a group fired.
Preview Replacements
Flip on Replace mode to see the result of a substitution applied to your whole test string. It supports the usual replacement tokens — $1 for numbered groups, $<name> for named groups, and $& for the full match — and you can copy the result with one click.
A Built-in Cheat Sheet
A collapsible quick reference covers the syntax you reach for most — character classes, anchors, quantifiers, alternation, groups, look-ahead, and more — so you do not have to leave the page to remember how to write a named group or a non-capturing one.
Who It's For
- Developers building input validation or search-and-replace logic
- Data wranglers extracting fields from logs, CSVs, and free-form text
- Anyone learning regex who wants a fast, visual feedback loop
If your text is structured data, pair the Regex Tester with tools like the JSON Formatter or Text Diff Checker to inspect and compare results.
Privacy First
Like every tool on PowerDev.Tools, the Regex Tester runs entirely in your browser using the native JavaScript engine. Your patterns and test data never leave your machine — no server-side processing, no tracking, and no accounts required. Install the PWA and it works offline too.
Try It Out
Head over to the Regex Tester and give it a try. As always, it is free, private, and works offline.
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