a twenty-four character document id
Matches a twenty-four character document id. It is anchored at both ends, so the whole string has to match. There are no capture groups.
Pattern
/^[0-9a-f]{24}$/i- Match scope
- the whole string
- Capture groups
- 0
- Flags
- i · ignore case
- What it catches in the first example
- 507f1f77bcf86cd799439011
Try it yourself
Type any text and the parts this expression catches are highlighted. It runs in your browser and is never sent anywhere.
507f1f77bcf86cd799439011
1 match
Examples that match
- 507f1f77bcf86cd799439011
Examples that do not match
- 507f1f77bcf86cd79943901
- zzzf1f77bcf86cd799439011
Other expressions in this group
^\d*[02468]$an even number^\s*$a blank line^\d{4}-W(?:0[1-9]|[1-4]\d|5[0-3])$an ISO week number, up to week 53^#(?:[0-9a-f]{4}|[0-9a-f]{8})$a hex colour that carries alpha^\d{4}(?:[ -]?\d{4}){3}$a card number written in four blocks of four^[A-Z]{3}$a three-letter currency code^0x[0-9a-f]+$a hex number written with the 0x prefix^[0-9a-f]{64}$a sixty-four character hashHow to read this
- With ^ and $ around it, the whole string must match; without them the match can sit anywhere. Always anchor an expression you use for validation.
- Round brackets ( ) capture what they wrap. When you only need grouping, write (?: ) so the numbering of later groups does not shift.
- Every expression here is checked against its examples. Even so, "looks like an email" and "is a real inbox" remain different questions.
- Nested open-ended repeats such as (a+)+ can blow up on certain inputs. Look for that shape before pasting someone else’s expression into your code.
Frequently asked questions
Q. What is the regex for a twenty-four character document id?
^[0-9a-f]{24}$, with the i flag.
Q. Which strings match?
Text like 507f1f77bcf86cd799439011 matches; text like 507f1f77bcf86cd79943901 does not.
Q. Does the whole string have to match?
Yes. It is wrapped in ^ and $, so nothing but a full match passes.
Q. How do I use what it caught?
There are no capture groups, so only the whole match (match[0]) comes back. Wrap the part you need in brackets to capture it.