Is this cheatsheet JS-specific?

It aligns with ECMAScript regex — POSIX or PCRE-only features may differ or need alternate syntax.

What does ^ and $ mean?

^ anchors the start of the input (or line with m flag); $ anchors the end — critical for validating entire strings vs substrings.

When do I need lookaheads?

Use (?=...) / (?!...) when you must assert context without consuming characters, such as passwords requiring digits ahead.

DotAll lets . match newline characters — essential for multiline log parsing in JS.

How do non-capturing groups help?

(?:...) groups alternatives without creating numbered backreferences, keeping replace strings simpler.

Why escape dashes in character classes?

Place - first or last inside [] to mean literal dash; otherwise it defines a range like a-z.

Can I Unicode-match names?

Use \p{L} with u flag for Unicode property escapes when matching international text.

Where do I test live?

Pair this page with the Regex Tester tool in the same suite for interactive validation.

Regex Cheatsheet

Dev Live

Quick reference for regex tokens, flags and lookarounds.

About this tool

Regex Cheatsheet — Quick reference for regex tokens, flags and lookarounds. Free, fast and private. Runs entirely in your browser at Quick Calci Tools.

Examples

Common scenarios for the Regex Cheatsheet.

Digit runs

pattern: \d+

Matches one or more ASCII digits.

Non-greedy match

pattern: <.*?>
flags: g

Lazy quantifier stops at first closing angle bracket.

Who uses the Regex Cheatsheet?

Common scenarios and audiences for this tool.

Junior developers

Decode cryptic patterns in code review without leaving the browser.

Support engineers

Tune customer log filters using correct boundary tokens.

Interview candidates

Refresh syntax minutes before live-coding phone screens.

No-code admins

Understand what marketing’s redirect rules actually mean.

Teachers

Hand out a stable link alongside regex homework.

Frequently asked questions

Everything you need to know about the Regex Cheatsheet.