How to replace plain URLs with links?

First off, rolling your own regexp to parse URLs is a terrible idea. You must imagine this is a common enough problem that someone has written, debugged and tested a library for it, according to the RFCs. URIs are complex – check out the code for URL parsing in Node.js and the Wikipedia page on URI schemes.

There are a ton of edge cases when it comes to parsing URLs: international domain names, actual (.museum) vs. nonexistent (.etc) TLDs, weird punctuation including parentheses, punctuation at the end of the URL, IPV6 hostnames etc.

I’ve looked at a ton of libraries, and there are a few worth using despite some downsides:

  • Soapbox’s linkify has seen some serious effort put into it, and a major refactor in June 2015 removed the jQuery dependency. It still has issues with IDNs.
  • AnchorMe is a newcomer that claims to be faster and leaner. Some IDN issues as well.
  • Autolinker.js lists features very specifically (e.g. “Will properly handle HTML input. The utility will not change the href attribute inside anchor () tags”). I’ll thrown some tests at it when a demo becomes available.

Libraries that I’ve disqualified quickly for this task:

  • Django’s urlize didn’t handle certain TLDs properly (here is the official list of valid TLDs. No demo.
  • autolink-js wouldn’t detect “” without http://, so it’s not quite suitable for autolinking “casual URLs” (without a scheme/protocol) found in plain text.
  • Ben Alman’s linkify hasn’t been maintained since 2009.

If you insist on a regular expression, the most comprehensive is the URL regexp from Component, though it will falsely detect some non-existent two-letter TLDs by looking at it.

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