Extracting top-level and second-level domain from a URL using regex

Question

How can I extract only top-level and second-level domain from a URL using regex? I want to skip all lower level domains. Any ideas?

Answer 1

With capturing groups you can achieve some magix.

For example, consider the following javascript:

let hostname = 'test.something.else.be';
let domain = hostname.replace(/^.+\.([^\.]+\.[^\.]+)$/, '$1');

document.write(domain);

This will result in a string containing 'else.com'. This is because the regex itself will match the complete string and the capturing group will be mapped to $1. So it replaces the complete string 'test.something.else.com' with '$1' which is actually 'else.com'.

The regex isn't pretty and can probably be made more dynamic with things like {3} for defining how many levels deep you want to look for subdomains, but this is just an illustration.

Answer 2

If you need to be more specific:

/\.(?:nl|se|no|es|milru|fr|es|uk|ca|de|jp|au|us|ch|it|io|org|com|net|int|edu|mil|arpa)/

Based on http://www.seobythesea.com/2006/01/googles-most-popular-and-least-popular-top-level-domains/

Answer 3

Since TLDs now include things with more than three-characters like .wang and .travel, here's a regex that satisfies these new TLDs:

([^.\s]+\.[^.\s]+)$

Strategy: starting at the end of the string, look for one or more characters that aren't periods or whitespace, followed by a single period, followed by one or more characters that aren't periods or whitespace.

http://regexr.com/3bmb3

Answer 4

Here's my idea,

Match anything that isn't a dot, three times, from the end of the line using the $ anchor.

The last match from the end of the string should be optional to allow for .com.au or .co.nz type of domains.

Both the last and second last matches will only match 2-3 characters, so that it doesn't confuse it with a second-level domain name.

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Regex:

[^.]*\.[^.]{2,3}(?:\.[^.]{2,3})?$

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Demonstration:

Regex101 Example

Answer 5

if you want all specific Top Level Domain name then you can write regular expression like this:

[RegularExpression("^(https?:\\/\\/)?(([\\w]+)?\\.?(\\w+\\.((za|zappos|zara|zero|zip|zippo|zm|zone|zuerich|zw))))\\/?$", ErrorMessage = "Is not a valid fully-qualified URL.")]

You can also put more domain name from this link:

https://www.icann.org/resources/pages/tlds-2012-02-25-en

Answer 6

The following regex matches a domain with root and tld extractions (named capture groups) from a url or domain string:

(?:\w+:\/{2})?(?<cs_domain>(?<cs_domain_sub>(?:[\w\-]+\.)*?)(?<cs_domain_root>[\w\-]+(?<cs_domain_tld>(?:\.\w{2})?(?:\.\w{2,3}|\.xn-+\w+|\.site|\.club))))\|

It's hard to say if it is perfect, but it works on all the test data sets that I have put it against including .club, .xn-1234, .co.uk, and other odd endings. And it does it in 5556 steps against 40k chars of logs, so the efficiency seems reasonable too.