Are these patterns production-ready?

They are solid starting points for common cases. The classic example: fully RFC-compliant email validation is practically impossible in pure regex — the patterns here cover the pragmatic 99%, not the adversarial 1%.

Will these patterns work in every language?

The core syntax (classes, quantifiers, groups, anchors) is nearly universal. Advanced features like lookbehind or named groups vary by engine — verify JavaScript behavior in the Regex Tester.

How do I adapt a pattern to my case?

Copy it into the Regex Tester, paste a sample of your real text, then tighten the pattern until only the parts you want are highlighted.

Regex Cheat Sheet — Guide

A complete regex cheat sheet — common regular expression syntax, quantifiers, flags and character classes with examples.

What it is and when to use it

Regex syntax is easy to forget precisely because it is dense: character classes, quantifiers, anchors and groups are all written in punctuation. This cheat sheet collects the constructs you actually reach for — ready-made patterns for emails, URLs and dates, the common character classes, and lookahead examples — so you copy a working starting point instead of rebuilding it from memory.

A cheat sheet of common regular expressions for when you have forgotten the syntax.

How to use it

Find the syntax you need by category
Copy the fragment
Verify it in the Regex Tester

Things that trip people up

Syntax is JavaScript-flavoured (the \d, \w and [...] classes, and groups). Features such as lookbehind and named capture are engine-specific — test in the Regex Tester before assuming another language behaves the same
This is a construct reference, not a full grammar: less common features such as atomic groups or possessive quantifiers are intentionally out of scope

Questions people ask

Are these patterns production-ready?: They are solid starting points for common cases. The classic example: fully RFC-compliant email validation is practically impossible in pure regex — the patterns here cover the pragmatic 99%, not the adversarial 1%.
Will these patterns work in every language?: The core syntax (classes, quantifiers, groups, anchors) is nearly universal. Advanced features like lookbehind or named groups vary by engine — verify JavaScript behavior in the Regex Tester.
How do I adapt a pattern to my case?: Copy it into the Regex Tester, paste a sample of your real text, then tighten the pattern until only the parts you want are highlighted.

Next steps

Open the Regex Cheat Sheet tool

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