a compressed IPv6 address
Matches a compressed IPv6 address. It is anchored at both ends, so the whole string has to match. There are 4 capture groups.
Pattern
/^([0-9a-fA-F]{1,4}(:[0-9a-fA-F]{1,4})*)?::([0-9a-fA-F]{1,4}(:[0-9a-fA-F]{1,4})*)?$/- Match scope
- the whole string
- Capture groups
- 4
- What it catches in the first example
- ::1
Try it yourself
Type any text and the parts this expression catches are highlighted. It runs in your browser and is never sent anywhere.
::1
1 match
Examples that match
- ::1
- fe80::
- 2001:db8::1
Examples that do not match
- 192.168.0.1
- 2001:db8:0:0:0:0:0:1
- hello
Other expressions in this group
^(\d{1,3}\.){3}\d{1,3}/\d{1,2}$an IPv4 address with a CIDR prefix^01[016789]-?\d{3,4}-?\d{4}$a Korean mobile number^[가-힣]{2,5}$a Hangul name of two to five syllables^\d{5}(-\d{4})?$a US ZIP code^\d{3}-\d{2}-\d{5}$a Korean business registration number^[a-z]+\/[a-zA-Z0-9][a-zA-Z0-9.+-]*$a MIME type^data:[a-z]+\/[a-z0-9.+-]+;base64,[A-Za-z0-9+/]+=*$a base64 data: URI^(\S+\s+){4}\S+$a five-field cron expressionHow 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 compressed IPv6 address?
^([0-9a-fA-F]{1,4}(:[0-9a-fA-F]{1,4})*)?::([0-9a-fA-F]{1,4}(:[0-9a-fA-F]{1,4})*)?$.
Q. Which strings match?
Text like ::1 matches; text like 192.168.0.1 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 4 capture groups, so you can read them from match[1] onwards.