Regex to match a slug?

Question

I'm having trouble creating a Regex to match URL slugs (basically, alphanumeric "words" separated by single dashes)

this-is-an-example

I've come up with this Regex: /[a-z0-9\-]+$/ and while it restricts the string to only alphanumerical characters and dashes, it still produces some false positives like these:

-example example- this-----is---an--example -

I'm quite bad with regular expressions, so any help would be appreciated.

What programming language?

zzzzBov
– zzzzBov

2013-10-08 19:17:39 +00:00
Commented Oct 8, 2013 at 19:17 — zzzzBov
– zzzzBov, Commented Oct 8, 2013 at 19:17
@zzzzBov I'm using PHP (with the preg_match function).

federicot
– federicot

2013-10-08 19:19:52 +00:00
Commented Oct 8, 2013 at 19:19 — federicot
– federicot, Commented Oct 8, 2013 at 19:19

Rohit Jain · Accepted Answer · 2013-10-08 19:20:02Z

75

You can use this:

/^ [a-z0-9]+ # One or more repetition of given characters (?: # A non-capture group. - # A hyphen [a-z0-9]+ # One or more repetition of given characters )* # Zero or more repetition of previous group $/

This will match:

A sequence of alphanumeric characters at the beginning.
Then it will match a hyphen, then a sequence of alphanumeric characters, 0 or more times.

edited Oct 8, 2013 at 19:20

answered Oct 8, 2013 at 19:14

Rohit Jain

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9 Comments

federicot Over a year ago

Great! This works almost as I want. Can you tweak it in order to match a single word too? (I forgot to mention that single words are considered valid slugs too).

anubhava Over a year ago

@fedeetz: Just replace last + with * (0 or more matches)

Danon Over a year ago

@mathieug First, capturing group isn't wanted by the author, so what's the point of having it in your results? Secondly, The group is repeated, so with a repeated capturing group, only the last repetition would captured.

InsOp Over a year ago

for the lazy: /^[a-z0-9]+(?:-[a-z0-9]+)*$/

danronmoon Over a year ago

@Yandiro /^[a-z0-9]+(?:[_-][a-z0-9]+)*$/

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Aurovrata · Accepted Answer · 2021-10-27 11:37:57Z

A more comprehensive regex that will match both ascii and non-ascii characters in slugs would be,

/^ # start of string [^\s!?\/.*#|] # exclude spaces/tabs/line feed.. as well as reserved characters !?/.*# + # match one or more times $/ # end of string

for good measure we exclude the reserved URL characters.

so for example, the above will match

une-ecole_123-soleil une-école_123-soleil une-%C3%A9cole-123_soleil

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