A regex tester online that shows you what your pattern actually does. Type an expression, paste your test string, and watch every match highlight as you type — with capture groups, flags and a plain-English breakdown of each token. Nothing is uploaded; the whole engine runs in your browser.
No signupRuns in your browserNothing uploaded
Regex TesterLive
This tool is built for a wider screen — scroll sideways inside the frame, or turn your device.
How to use it
Four steps to a result
Write your pattern
Type the expression between the delimiters. Toggle flags like g, i and m to change how matching behaves.
Paste a test string
Drop in real sample text — a log line, a CSV row, a block of HTML. Matches highlight instantly as you edit either side.
Inspect the matches
Every match lists its index, full value and each numbered or named capture group, so you can see exactly what your pattern grabbed.
Copy it into your code
Grab the finished expression, or use the explainer panel to document what each part of the pattern is doing before you ship it.
Questions
Frequently asked questions
Type your pattern into the expression field and paste sample text into the test area. Matches highlight live as you type, and each one is listed below with its position and capture groups. There is no run button — results update on every keystroke.
It uses the JavaScript (ECMAScript) engine built into your browser, the same one that runs RegExp in Node and the DOM. Patterns that work here work in JavaScript and TypeScript directly. PCRE-only constructs like recursion or possessive quantifiers are not supported.
The three usual causes are a missing global flag when you expect multiple matches, an unescaped special character such as . or ?, and greedy quantifiers swallowing more than intended. The explainer panel breaks your pattern into tokens so you can see which part fails.
Anything wrapped in parentheses becomes a capture group, numbered from left to right. Named groups use the (?<name>...) syntax. Each match in the results list shows every group it captured, so you can confirm the right substring landed in the right slot.
No. The regex tester runs entirely in your browser — there is no backend and no network request. You can safely test patterns against production log lines, customer records or anything else sensitive.
Keep going
More free tools
Every one runs in your browser, with no account and nothing uploaded.