Regex tester · JavaScript flavour
Matches and capture groups light up as you type. Preview replacements and splits, read every token in plain English, and copy working code for five languages.
5 matches
What text.split(regex) returns. Captured groups are included in the array, marked in their group colour.
Type a pattern between the slashes and the test string on the left lights up: each match gets a vermilion or ochre wash, and every capture group is underlined in its own colour, the same colour its parentheses have in the pattern and its entry in the match table. Hover a row in the table to find that match in the text; click it to select it.
Matching runs in a Web Worker using your browser’s own JavaScript engine, so results are exactly what RegExp gives in your code. If a pattern backtracks catastrophically, the worker is stopped after one second instead of freezing the page.
Share copies a link that holds the pattern, flags and test text in the part of the address after #. Browsers never send that part to a server, and RegexQuill removes it from the address bar once the page has read it.
g finds every match; without it only the first one counts.i ignores case; m lets ^ and $ match at line breaks.s lets . match line breaks too.u turns on Unicode mode (needed for \p{…}); v adds set operations and emoji sequences.y only matches at lastIndex; d records group positions.An email regex can only check that an address looks right. To see whether your form really sends its confirmation mail, sign up with a free disposable inbox: no registration, hundreds of domains to choose from, and messages are deleted automatically after 3 days.
Temp Mail API for automated verification tests (opens in a new tab)
Get a temporary inbox (opens in a new tab)Regex rewrite rules in nginx, Apache or Cloudflare are easy to get subtly wrong. Follow a URL’s real redirect chain, check its security headers, or open the site in a disposable cloud browser on an isolated Linux desktop that is deleted after each session.
Redirect chain checker (opens in a new tab)Security headers check (opens in a new tab)All free tools (opens in a new tab)
Try the cloud browser (opens in a new tab)JavaScript (ECMAScript), using the engine of the browser you are on. That includes lookbehind, named groups, Unicode property escapes, the v flag and, in current browsers, pattern modifiers. The Code tab translates the pattern for Python, PHP, Go and Java and lists the differences that matter.
No. Parsing, matching and code generation all happen in your browser. A share link carries the pattern and text after the # in the address, a part that browsers never send to servers.
The pattern is probably backtracking catastrophically on this text: nested or overlapping quantifiers make the engine try an enormous number of ways to match. Matching runs in a worker that is stopped after one second. Open the pattern in the ReDoS checker to see which part causes it.
Matches alternate between a vermilion and an ochre wash so neighbouring matches stay distinct. Each capture group has its own colour, used for its parentheses in the pattern, its underline in the text, its column in the table and its part of the split preview.
Check the flags first: without g only the first match counts, and without m the anchors ^ and $ only match at the very start and end. In a string passed to new RegExp(), every backslash must be doubled; the Code tab writes that for you.