ISO Year-Week Regex Pattern
Validates an ISO 8601 year-week date (YYYY-Www, weeks 01-53).
Pattern
^\d{4}-W(?:0[1-9]|[1-4]\d|5[0-3])$Tested examples
2026-W012026-W521999-W182026-W542026-W02026W18Test it live
Live Regex TesterJS
0 matches/
/g
2026-W01 2026-W52 1999-W18
Use it in your language
Use it in
// JavaScript / Node.js
const regex = /^\d{4}-W(?:0[1-9]|[1-4]\d|5[0-3])$/;
const value = "2026-W01";
const isMatch = regex.test(value);
console.log(isMatch); // true / false
// Extract all matches
const matches = value.match(/^\d{4}-W(?:0[1-9]|[1-4]\d|5[0-3])$/g) || [];Tags
Frequently asked questions
How do I use the ISO Year-Week regex pattern in JavaScript?
Wrap the pattern in slashes: const re = /^\d{4}-W(?:0[1-9]|[1-4]\d|5[0-3])$/; — then call re.test(value) to check a single value, or value.match(re) to find matches. The "Use it in" snippets above give you the exact code for 9 languages.
Is this iso year-week regex production-ready?
Yes — every pattern in the library is tested against valid and invalid examples. Still, regex is one layer in a defense-in-depth strategy: pair it with server-side validation (e.g. Luhn for credit cards, mod-97 for IBAN, real DNS lookup for emails) for critical inputs.
Why does my pattern fail in another language?
Different regex engines (PCRE, Java, Python, Go's RE2) support slightly different syntax. The most common gotchas: lookbehinds (not in RE2), named groups syntax, and how backslashes need to be escaped inside string literals. The code snippets above already escape correctly for each language.
Can I edit this pattern and test it live?
Yes — use the live tester above. Type your test string and toggle flags (g, i, m, s, u, y) to see matches highlighted instantly, including capture groups.
Related patterns
See all Dates →Dates
ISO 8601 Date
YYYY-MM-DD format (e.g., 2023-12-25).
Dates24h Time HH:MM
Strict 24h time format (00:00 to 23:59).
DatesFrench Date Format
DD/MM/YYYY format (e.g., 25/12/2023).
DatesISO 8601 Datetime (with timezone)
Validates a full ISO 8601 datetime string with timezone (UTC Z or ±hh:mm). Standard for APIs.
DatesDate DD/MM or MM/DD
DD/MM/YYYY or MM/DD/YYYY format (no calendar validation).
DatesISO Date and Time
Full ISO 8601 DateTime with timezone.
Browse the full library — 250 tested regex patterns across 16 categories.