How to check if a string is a valid URL

Short answer

URL.canParse() returns true if the string is a complete address:

console.log(URL.canParse('https://example.com/page'));
console.log(URL.canParse('example.com'));
console.log(URL.canParse('not a url'));

Output:

true
false
false

Only http and https

Strings like javascript:alert(1) are also valid addresses. For links from users, also check the protocol:

const isWebUrl = (value) => {
  try {
    const url = new URL(value);
    return url.protocol === 'http:' || url.protocol === 'https:';
  } catch {
    return false;
  }
};
 
console.log(isWebUrl('https://example.com'));
console.log(isWebUrl('javascript:alert(1)'));
console.log(isWebUrl('ftp://files.example.com'));

Output:

true
false
false

Common mistake

A regular expression for URLs is easy to get wrong: it either rejects real addresses or lets bad ones through. The URL object parses addresses exactly like the browser does.

const naive = /^https?:\/\/\w+\.\w+$/;
 
console.log(naive.test('https://example.com/blog'));
console.log(URL.canParse('https://example.com/blog'));

Output:

false
true

Thanks for reading!

Short answer

Only http and https

Common mistake

Functions used in this recipe

Thanks for reading!