Patterns for common data Updated November 2026

Regex for alphanumeric

^[a-zA-Z0-9]+$ matches letters and digits only, with no spaces or symbols. \w is close but also allows the underscore, since it equals [a-zA-Z0-9_]. To allow Unicode letters and digits use ^[\p{L}\p{N}]+$ with the u flag.

Syntax

/^[a-zA-Z0-9]+$/

Examples

["abc123", "abc_123", "abc 123"].map(s => /^[a-zA-Z0-9]+$/.test(s))

Result: [true, false, false]

/^\w+$/.test("abc_123")

Result: true

\w allows the underscore.

"Hello World! 2024".toLowerCase().replace(/[^a-z0-9]+/g, "-").replace(/^-|-$/g, "")

Result: "hello-world-2024"

Make a slug: replace runs of non-alphanumerics with a dash, then trim dashes.

/^[\p{L}\p{N}]+$/u.test("Straße2")

Result: true

Common mistakes

Using \w and being surprised that underscores pass; write [a-zA-Z0-9] when they should not.
Writing [a-z0-9] without the i flag, which rejects uppercase letters.
Placing a hyphen in the middle of the class, as in [a-z0-9-_], which creates a range from 9 to _ that includes punctuation; put the hyphen first or last.
Forgetting the + and matching a single character only.

Practice Regex for alphanumeric

These drills check your answer on live data, free, no account needed.

SKU codesThe whole line must match. A SKU is three capital letters, a hyphen and four digits, optionally followed by a hyphen and a size: XS, S, M, L or XL.
URL slugsThe whole line must match. Match a URL slug: lowercase letters and digits in chunks joined by single hyphens. No hyphen at the start or end and no doubled hyphens.
Ranges: a letter and two digitsThe whole line must match. Match one lowercase letter followed by exactly two digits, like a12.

Questions

What is the regex for alphanumeric with spaces?

^[a-zA-Z0-9 ]+$. To forbid leading and trailing spaces use ^[a-zA-Z0-9]+(?: [a-zA-Z0-9]+)*$.

What is the regex for alphanumeric and underscore?

^\w+$ in JavaScript, or ^[a-zA-Z0-9_]+$ to be explicit and portable.

How do I check for alphanumeric in Excel or SQL?

Excel 365: =REGEXTEST(A1, "^[a-zA-Z0-9]+$"). PostgreSQL: col ~ '^[a-zA-Z0-9]+$'. MySQL: col REGEXP '^[a-zA-Z0-9]+$'. See the Excel and SQL pages for details.

Regex for letters onlyThe ^[a-zA-Z]+$ pattern for ASCII letters, a Unicode version with \p{L} and the u flag, allowing spaces between words, and stripping non-letters from text.
Regex for numbers onlyThe ^\d+$ pattern for digits-only strings, stripping everything that is not a digit, extracting numbers from text, and patterns for signed and decimal values.
Regex for usernameUsername regex patterns: the basic ^[a-zA-Z0-9_]{3,16}$ rule, a stricter letter-first variant, pulling @handles out of text, and a Unicode-friendly version.
Character classesWhat a character class matches, how ranges and negation work, what \d \w \s and their uppercase opposites mean, and what the dot does and does not match.