Regex Tester

A regular expression is quick to jot down in your head and hard to oversee in practice - does it really match what it should and nothing else? The Regex Tester answers that instantly: you type your pattern at the top, your test text below, and every match is highlighted right in the text. No guessing, no deploy to try it, you just see it.

You can toggle the flags individually and get a short explanation for each: g for all matches instead of just the first, i for case-insensitive, m for multiline, s for DotAll (the dot also matches newlines), u for Unicode and d for the start and end indices of groups. That way you also understand why a pattern sometimes matches and sometimes not.

Captured groups are broken down so you see which part of your expression caught which slice of text - indispensable when you use brackets to pull out data. A built-in cheat sheet explains the key building blocks from character classes through quantifiers to anchors, so you do not constantly look things up in a separate reference.

The real time-saver for German everyday life is the collection of 30+ ready-made patterns. It covers exactly the formats you otherwise break your teeth on: German IBAN with optional spaces, BIC, tax number and tax ID, VAT ID, commercial register number, postcode, landline and mobile numbers, German date, licence plate, court case reference, social security number, legal paragraph references, SEPA reference, currency amounts in German format and more. Each pattern comes with a sample text so you immediately see how it matches.

Because a badly built expression can bring the browser to its knees, a guard against catastrophic backtracking is built in: if evaluation runs too long, the tool aborts cleanly and warns you instead of freezing the tab. So you can safely try even risky patterns.

Everything runs in your browser with the JavaScript regex engine that your Node or frontend code also uses - what matches here matches there. Nothing is uploaded, nothing is stored. No account, no signup, no data leaving your device. Ideal for building, understanding and learning regular expressions.