sysop@hub:~/tools/regex-tester$

regex-tester

Regular expressions turn up in log searches, mail rules, grep, PowerShell and monitoring tools, and they are easier to write than to read. Type a pattern and some test text: the page shows what matches, says in plain words what each part of the pattern means, points out the usual mistakes, and writes the same pattern for other tools.

Pattern Replace with (optional)

Flags g find all matches i ignore case m ^ and $ at every line s dot also matches line breaks

Test text

what the pattern says

Every part of the pattern in order, with groups indented. Point at a line, or move to it with the Tab key, to see that part marked in the pattern.

traps

the same pattern elsewhere

Regex dialects differ. This is how the pattern is written and quoted for the tools admins use most, and what each of them does not support.

Nothing you type leaves the browser. The link in the address bar holds the pattern, the flags and up to 2,000 characters of the test text, so you can share a test: do not put passwords or personal data in a link you pass on. Matching runs in your browser's JavaScript engine, so grep, sed, .NET and Python can decide differently in details. The table above names the known differences, not every one. The explanation covers the common syntax. It does not cover every corner, such as Unicode property escapes, the u and v flags or sticky matching. Related: regex patterns library, log reader, Linux playground, PowerShell cheat sheet, Bash scripting cheat sheet.