Regex Cheat Sheet — Interactive Regular Expression Syntax Reference, Python & JavaScript Examples, Live Tester
Regex Cheat Sheet
Regex cheat sheet & live tester
Interactive regular expression cheat sheet with examples — test patterns like regex101, plus Python, JavaScript, Java, Perl, and more.
2 matches
Emails: alice@example.com and bob@asli.dev — not-an-email.
| # | Index | Match | Groups |
|---|---|---|---|
| 1 | 8 | alice@example.com | — |
| 2 | 30 | bob@asli.dev | — |
Common regex recipes
Click a recipe to load it into the tester — regex cheat sheet with examples for everyday patterns.
Regex syntax cheat sheet
Anchors
| Token | Meaning | Example |
|---|---|---|
| Start of string (or line with m flag) | ^Hello | |
| End of string (or line with m flag) | world$ | |
| Start of string only (Python/Perl/.NET; not JS) | — | |
| End of string (before final newline in some flavors) | — | |
| Word boundary | \bcat\b | |
| Not a word boundary | \Bcat |
Quantifiers
| Token | Meaning | Example |
|---|---|---|
| 0 or more (greedy) | a* | |
| 1 or more (greedy) | a+ | |
| 0 or 1 (greedy) | colou?r | |
| Exactly n times | \d{3} | |
| n or more times | \d{2,} | |
| Between n and m times | \d{2,4} | |
| 0 or more (lazy) | <.*?> | |
| 1 or more (lazy) | a+? | |
| 0 or 1 (lazy) | — | |
| Possessive + (Java/PCRE; not JS) | — |
Character classes
| Token | Meaning | Example |
|---|---|---|
| Any char except newline (unless s/dotall) | a.c | |
| Digit [0-9] | \d+ | |
| Non-digit | \D+ | |
| Word char [A-Za-z0-9_] | \w+ | |
| Non-word char | \W+ | |
| Whitespace | \s+ | |
| Non-whitespace | \S+ | |
| One of a, b, or c | [aeiou] | |
| Not a, b, or c | [^0-9] | |
| Range a to z | [A-Za-z] | |
| Any character including newline (JS trick) | — |
Groups & references
| Token | Meaning | Example |
|---|---|---|
| Capturing group | (\d{3}) | |
| Non-capturing group | (?:https?) | |
| Named capture (JS/Python/.NET/Java) | (?<year>\d{4}) | |
| Backreference to group 1 | (\w+)\s+\1 | |
| Named backreference | — | |
| Alternation (OR) | cat|dog |
Lookahead & lookbehind
| Token | Meaning | Example |
|---|---|---|
| Positive lookahead | \d+(?=px) | |
| Negative lookahead | foo(?!bar) | |
| Positive lookbehind | (?<=\$)\d+ | |
| Negative lookbehind | (?<!@)\b\w+ |
Flags / modifiers
| Token | Meaning | Example |
|---|---|---|
| Global — find all matches (JS) | — | |
| Case-insensitive | /hello/i | |
| Multiline — ^/$ match line ends | — | |
| Dotall — . matches newline (JS/Python re.S) | — | |
| Unicode mode (JS) | — | |
| Sticky — match from lastIndex (JS) | — | |
| Python flag constants | — | |
| Inline flags (many flavors) | — |
Escapes & special
| Token | Meaning | Example |
|---|---|---|
| Literal backslash | — | |
| Tab, newline, carriage return | — | |
| Hex character | \x41 → A | |
| Unicode code point (JS) | \u00A9 | |
| Unicode property letter (with u) | — | |
| Quote literal span (Java/Perl) | — |
Language flavors
Python regex cheat sheet, JavaScript / JS, Java, Perl, C# /.NET, bash, R, SQL, PowerShell, and editor notes.
JavaScript regex cheat sheet essentials for browser and Node.
- Use /pattern/flags or new RegExp(pattern, flags).
- Remember lastIndex with the g flag when reusing a RegExp.
- Named groups: /(?<year>\d{4})/u — access match.groups.year.
const re = /\b\w+@\w+\.\w+/gi; const text = "a@b.com and c@d.org"; console.log([...text.matchAll(re)]);
Regex Cheat Sheet — Syntax, Examples & Tester
Free interactive regex cheat sheet with a live tester. Includes a Python regex cheat sheet, JavaScript / JS regex cheat sheet, Java, Perl, C#, bash/grep, and R notes — a practical regular expression cheat sheet with examples.
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Frequently asked questions
- What is a regex cheat sheet?
- A regex cheat sheet (regular expression cheat sheet) is a quick reference for syntax tokens like ^, $, \d, quantifiers, groups, and lookarounds — often paired with a live tester and language-specific notes for Python, JavaScript, Java, and more.
- Is this a Python regex cheat sheet too?
- Yes. Besides the general regex syntax cheat sheet, this page includes Python re module tips and examples (raw strings, flags, search/findall/sub), plus JavaScript, Java, Perl, C#/.NET, bash/grep, and R notes.
- How do I test a regex pattern with examples?
- Use the live tester: enter a pattern and flags, paste a test string, and see highlighted matches, indexes, and capture groups — similar to regex101-style debugging on a printable online cheat sheet.
- Do Java and JavaScript regex work the same?
- Most core tokens are shared, but flavors differ: Java strings need double escaping, possessive quantifiers exist in Java/PCRE, and JS has g/y/u flag behavior. Use the language tabs for flavor-specific cheat sheet notes.
- Can I use this as a printable regex cheat sheet?
- Yes — open the page and print (Ctrl/Cmd+P) for a printable regex cheat sheet PDF via your browser’s print-to-PDF. The syntax tables and recipes print cleanly.
Looking for a python regex cheat sheet with examples, javascript regex cheat sheet, Linux/bash/grep notes, or a printable regex cheat sheet PDF? Use the tester and tables above, then print to PDF. Covers anchors, quantifiers, character classes, groups, lookarounds, and common recipes — a complete regex expression cheat sheet for daily coding.