Live match highlighting. No page reloads, no excuses.
Regular expressions are a pattern-matching language embedded in almost every programming language and text editor. The syntax looks like someone sat on a keyboard, but once it clicks, it's one of the most useful tools in the bag.
This tester lets you write a pattern, set flags, and immediately see which parts of your test string match - highlighted inline, with match counts and captured groups listed separately. Live updates as you type, so you can iterate quickly.
The engine is the browser's native RegExp implementation - no server,
no extra library. What you see is what JavaScript's regex engine actually produces,
which is what you'll get in a JS codebase. If you're writing patterns for a different
language (Python, Perl, PCRE), flag semantics may differ slightly.
g (global) finds all matches instead of stopping at the first.
i makes the match case-insensitive.m makes ^
and $ match start/end of each line rather than the whole string.
s makes . match newlines too.