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Alphanumeric regex tester
Test letters and numbers only, with optional spaces, underscores and hyphens, Unicode letters or a length limit. Pick a preset, edit the regex and paste strings one per line. Copy JavaScript, Python or an HTML pattern when you are ready.
One or more ASCII letters or digits; does not require both. Spaces and punctuation are excluded.
3 of 6 match
- Match
abc123 - Match
ABC - Match
123 - No match
abc 123 - No match
user_name - No match
café
HTML pattern uses the v flag and matches the entire input. Add required to reject empty values. The Unicode Python snippet requires the third-party regex module; other snippets use re.ASCII. Validate again on the server.
Alphanumeric regex patterns
Choose a format that fits your input. The default pattern ^[A-Za-z0-9]+$ matches ASCII letters and digits only. Each preset is checked against its match and no-match samples.
| Preset | Regex | Match / no match examples | Notes |
|---|---|---|---|
| ASCII letters and digits only | ^[A-Za-z0-9]+$ | Match: abc123, ABC, 123No match: abc 123, user_name, café; empty string | One or more ASCII letters or digits; does not require both. Spaces and punctuation are excluded. |
| Alphanumeric with spaces | ^[A-Za-z0-9 ]+$ | Match: abc 123, Hello World, abc123 , No match: abc_123, abc 123, café; empty string | Allows ordinary spaces, including leading, trailing and all-space values. Trim first and reject an empty result when needed; tabs are excluded. |
| Alphanumeric plus underscore and hyphen | ^[A-Za-z0-9_-]+$ | Match: user_name, my-slug123, abc123No match: abc 123, user.name, café; empty string | For slugs and handles; allows separators anywhere, including separator-only values. Add position rules if your application needs them. |
| At least one letter AND one digit | ^(?=.*[A-Za-z])(?=.*\d)[A-Za-z0-9]+$ | Match: abc123, a1, 9ZNo match: abcdef, 123456, abc 123; empty string | Two lookaheads require an ASCII letter and a digit; only ASCII alphanumeric characters may appear. |
| Unicode letters and digits | ^[\p{L}\p{N}]+$ | Match: café123, 東京１２３, مرحبا١٢٣, abc123No match: café 123, user_name, 😀, é; empty string | JavaScript requires u; HTML pattern uses v. Python: use the regex module for \p properties, or [^\W_]+ with standard re. Combining marks are excluded; consider NFC normalization for decomposed accents. |
| Fixed length range: 6-12 characters | ^[A-Za-z0-9]{6,12}$ | Match: abc123, ABCdef123456, 123456No match: abc12, ABCdef1234567, abc 123; empty string | Requires 6 through 12 ASCII letters or digits. For exactly 8 characters, replace {6,12} with {8}. |
Alphanumeric regex in an HTML form
<label for="code">Letters and numbers only</label>
<input id="code" name="code" type="text" pattern="[A-Za-z0-9]+" required>A text input can enforce letters and numbers with the pattern attribute; HTML matches the entire value and uses the v flag, which supports Unicode properties. Add required to reject an empty value. The handle preset escapes the literal hyphen for v-mode character classes. Trim spaces before validation if your field requires it. Validate again on the server.
Why [a-zA-Z0-9] and not \w
\w also matches underscore. In Python and some other engines it includes Unicode letters and numbers; JavaScript primarily uses ASCII word characters, with a few extra case-folding matches under iu. Use [a-zA-Z0-9] for an explicit ASCII rule, or Unicode properties with the u flag for international input.
References: HTML pattern rules, JavaScript Unicode properties and Python re documentation.
Alphanumeric regex FAQ
What regex matches alphanumeric characters only?
Use ^[A-Za-z0-9]+$ for one or more ASCII letters or digits. It rejects spaces, underscores, punctuation and empty strings. It does not require both a letter and a digit.
How do I allow spaces in an alphanumeric regex?
Use ^[A-Za-z0-9 ]+$ to allow ordinary spaces alongside ASCII letters and digits. It also accepts leading, trailing and all-space values. Trim first and reject an empty result if those are unwanted. Tabs and line breaks are not allowed.
How do I require at least one letter and one number?
Use ^(?=.*[A-Za-z])(?=.*\d)[A-Za-z0-9]+$. The two lookaheads require a letter and a digit; the final character class rejects spaces and punctuation.
How do I match Unicode letters and digits?
Use /^[\p{L}\p{N}]+$/u in JavaScript. Python needs the third-party regex module for these properties, or use [^\W_]+ with standard re for Unicode alphanumeric characters. HTML pattern uses the v flag. Decomposed accents contain combining marks, so normalize to NFC first when appropriate; standalone marks are excluded.
Should I validate alphanumeric input on the server?
Yes. Browser validation can be bypassed. Apply the same character, length and normalization rules on the server. Add required in HTML if the value must not be empty.
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