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Regular Expression Tester

Write an expression and instantly see matches, groups, the replacement and a part-by-part breakdown in plain English. Plus “should match / should not match” tests.

What the tool can do

Match highlighting, a table of groups with names and positions, replacement with $1, $<name> and $&.
A part-by-part explanation of the expression in plain language: what each parenthesis, class and quantifier does.
Test mode: mark examples with + (should match) and − (should not match) and immediately see which of them the expression handles wrongly.
Protection against “catastrophic backtracking”: a heavy expression is interrupted after 2.5 seconds, and the page does not freeze.
13 ready-made patterns: email, Russian phone number, dates, IP, colors, hashtags and others.
Ready-made code for JavaScript, Python, PHP, Go, Java and C# with correct escaping.

Your browser's regular expression engine is used (JavaScript syntax). In other languages some features may differ, for example lookbehind in older versions.