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Regex Cheat Sheet
Updated October 2026 · Bookmark it for later — once you've written a pattern, verify it in the online regex tester
Character Matching
| Pattern | Meaning |
|---|
. | Any character except a newline |
\d / \D | Digit / non-digit |
\w / \W | Letter, digit or underscore / the opposite |
\s / \S | Whitespace character / non-whitespace |
[abc] | Any one of a, b or c |
[^abc] | Any character except a, b or c |
[0-9] / [a-z] | Character range |
Quantifiers
| Pattern | Meaning |
|---|
* | 0 or more times |
+ | 1 or more times |
? | 0 or 1 time |
{n} / {n,} / {n,m} | Exactly n times / at least n times / between n and m times |
*? / +? | Non-greedy (match as few as possible) |
Anchors and Groups
| Pattern | Meaning |
|---|
^ / $ | Start / end of string |
\b | Word boundary |
(abc) | Capturing group — reference it with $1 |
(?:abc) | Non-capturing group |
a|b | Alternation (or) |
(?=abc) / (?!abc) | Positive lookahead / negative lookahead |
Common Examples (Copy & Paste)
| Use case | Pattern |
|---|
| Mobile number (mainland China) | ^1[3-9]\d{9}$ |
| Email | ^[\w.-]+@[\w.-]+\.\w+$ |
| URL | ^https?://[\w.-]+(:\d+)?(/.*)?$ |
| Chinese ID number (18 digits) | ^[1-9]\d{5}(19|20)\d{2}(0[1-9]|1[0-2])(0[1-9]|[12]\d|3[01])\d{3}[\dXx]$ |
| IPv4 | ^(\d{1,3}\.){3}\d{1,3}$ |
| Date YYYY-MM-DD | ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$ |
| Password (8+ chars, letters and digits) | ^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$ |
| Trim leading/trailing whitespace | ^\s+|\s+$ (replace with an empty string) |
Watch Out For
1. Don't chase the "perfect regex" for email/URL. A spec-complete email regex runs to thousands of characters — good enough is good enough; the real validation is sending a verification email.
2. Beware of catastrophic backtracking: nested quantifiers like (a+)+$ against a long string can hang forever. Add concrete bounds or switch to non-greedy matching.
3. Before splicing user input into a regex, run it through an escape function for special characters — never concatenate it raw.