parseUri 1.2: Split URLs in JavaScript

I've just updated parseUri. If you haven't seen the older version, parseUri is a function which splits any well-formed URI into its parts, all of which are optional. Its combination of accuracy, flexibility, and brevity is unrivaled.


  • Comprehensively splits URIs, including splitting the query string into key/value pairs. (Enhanced)
  • Two parsing modes: loose and strict. (New)
  • Easy to use (returns an object, so you can do, e.g., parseUri(uri).anchor).
  • Offers convenient, pre-concatenated components (path = directory and file; authority = userInfo, host, and port; etc.)
  • Change the default names of URI parts without editing the function, by updating parseUri.options.key. (New)
  • Exceptionally lightweight (1 KB before minification or gzipping).
  • Released under the MIT License.


Older versions of this function used what's now called loose parsing mode (which is still the default in this version). Loose mode deviates slightly from the official generic URI spec (RFC 3986), but by doing so allows the function to split URIs in a way that most end users would expect intuitively. However, the finer details of loose mode preclude it from properly handling relative paths which do not start from root (e.g., "../file.html" or "dir/file.html"). On the other hand, strict mode attempts to split URIs according to RFC 3986. Specifically, in loose mode, directories don't need to end with a slash (e.g., the "dir" in "/dir?query" is treated as a directory rather than a file name), and the URI can start with an authority without being preceded by "//" (which means that the "" in "" is treated as the host, rather than part of the directory path).

Since I've assumed that most developers will consistently want to use one mode or the other, the parsing mode is not specified as an argument when running parseUri, but rather as a property of the parseUri function itself. Simply run the following line of code to switch to strict mode:

parseUri.options.strictMode = true;

From that point forward, parseUri will work in strict mode (until you turn it back off).

The code:

// parseUri 1.2.2
// (c) Steven Levithan <>
// MIT License

function parseUri (str) {
	var	o   = parseUri.options,
		m   = o.parser[o.strictMode ? "strict" : "loose"].exec(str),
		uri = {},
		i   = 14;

	while (i--) uri[o.key[i]] = m[i] || "";

	uri[] = {};
	uri[o.key[12]].replace(o.q.parser, function ($0, $1, $2) {
		if ($1) uri[][$1] = $2;

	return uri;

parseUri.options = {
	strictMode: false,
	key: ["source","protocol","authority","userInfo","user","password","host","port","relative","path","directory","file","query","anchor"],
	q:   {
		name:   "queryKey",
		parser: /(?:^|&)([^&=]*)=?([^&]*)/g
	parser: {
		strict: /^(?:([^:\/?#]+):)?(?:\/\/((?:(([^:@]*)(?::([^:@]*))?)?@)?([^:\/?#]*)(?::(\d*))?))?((((?:[^?#\/]*\/)*)([^?#]*))(?:\?([^#]*))?(?:#(.*))?)/,
		loose:  /^(?:(?![^:@]+:[^:@\/]*@)([^:\/?#.]+):)?(?:\/\/)?((?:(([^:@]*)(?::([^:@]*))?)?@)?([^:\/?#]*)(?::(\d*))?)(((\/(?:[^?#](?![^?#\/]*\.[^?#\/.]+(?:[?#]|$)))*\/?)?([^?#\/]*))(?:\?([^#]*))?(?:#(.*))?)/

You can download it here.

parseUri has no dependencies, and has been tested in IE 5.5–7, Firefox, Opera 9.21, Safari 3.0.1 beta for Windows, and Swift 0.2.

178 thoughts on “parseUri 1.2: Split URLs in JavaScript”

  1. Nice function. I miss the ability to get the query string as a list of key/value pairs, with a second argument to specify the parameter separator (with the ampersand by default). It’ll make the code a bit longer but the function would become much more complete.

  2. Hi Iván, thanks. parseUri already returns key/value pairs for the query string in an object called queryKey. For example, to access the value of a query key called “search” you could write parseUri(uri)

    You can see this in action on the test page, when you click the Parse button. Does that meet your needs, or were you thinking of something different?

  3. Sorry Steve, I didn’t notice it. That was exactly what I was talking about!
    However, a minor improvement would be to accept as optional second parameter a string which holds in each char a possible argument separator, most people use the ampersand but according to the RFC any char except ‘?’ and ‘#’. See my post

    I use myself the semi-colon ‘;’ as argument separator in some projects, since there is no need to escape it when used in XML/XHTML documents.

  4. Iván, I have no plans to support arbitrary delimiters in the query string because that would significantly complicate the code for the benefit of probably less than 0.1% of developers, and as you noted in your blog post, server side languages like PHP,, etc. generally don’t support delimiters other than “&” without special configuration, if at all.

    However, it would be easy to manually change the code to support both “&” and “;” delimiters in your personal copy. Just change /&?([^&=]*)=?([^&]*)/g from within the uri.query.replace() statement to /[&;]?([^&;=]*)=?([^&;]*)/g (or, to support only semicolons, use /;?([^;=]*)=?([^;]*)/g).

    In any case, this does not affect the main URI parsing (only the splitting of the query string into key/value pairs), so you could also implement a separate function to specifically work with the query string with maximum flexibility.

  5. Steve,

    I get your point and quite agree with it. What about placing the query RE in the options object so it can be easily modified by those with especial needs?

  6. @Iván Montes,

    Good call. I’ve gone ahead and moved the query regex as well as the query object’s name into the options object and upped the version number from 1.1 to 1.2. Thanks for the suggestion.

  7. Hey Steven,

    I couldn’t find any contact info so I’m just leaving a message here. I’m the maintainer of the CFJSON project and I’m trying to fix some things and would benefit from some regexp help and I know you’re quite good with them. If you think you could give me a hand shoot me an email (I put my email in the comment form) and I’ll tell you what I’m trying to fix. Something tells me you’ll be able to solve my problem without too much effort. Thanks in advance.

  8. Just as a possibility, if you create an anchor, assign the url as href, then you can access the anchor’s host,port,protocol,search,hash. This worked in FF dunno if it will work in the rest. I’m just saying this because it might make your code shorter 🙂

    I hope it helped

  9. @Ariel Flesler:

    It definitely would not make the code shorter, if you wanted to keep the same functionality as is currently provided. But still, that’s an interesting idea, if it works. 😉

  10. It looks like it doesn’t support the correct / standard URL parameter delimiter which is actually the ampersand entity ‘&amp;’ not a raw ampersand ‘&’. That’s precisely the functionality I am looking for as I’m getting an annoying error cropping up with one of my scripts that just uses a plain javascript split on ‘&’.

    That said, here are some of the top 10 xhtml errors:
    1. The use of a raw amperstand in a link query string. The w3c validator reports this as “cannot generate system identifier for general entity” because you’ve tried to create a new entity &xxxxxxx and not an encoded & amp ; in the string. Replace all & with &amp; in urls.

  11. As Safari 2.0 users may have noticed, the ‘queryString’ part isn’t filled because this version does not support a function as second parameter of String.prototype.replace() 🙁

  12. I get the following error using your code

    o has no properties

    [Break on this error] m = o.parser[o.strictMode ? “strict” : “loose”].exec(str),

    Please let me know.

    Thanks in advance!

  13. @Raj, yes, the demo uses the same code, which you could have easily verified yourself (the source files are uncompressed). Your URL does not contain a q key in the query, so the line of code you posted above is working correctly.

  14. Steven,

    My apologies. Initially, I felt some apprehension about browsing straight to the JS files in the demo. Just being respectful.

    Then I got over it. 🙂


  15. Thank you thank you thank you! In a short few weeks I’ve built at least two functions on top of this little gem and all my pages have components that will depend on them. Such a blessing!

  16. I *love* this function, it is so incredibly powerful and helpful! Thank you so much for it.

    For an open-source project I’m working on, I needed this same functionality inside of a Flash SWF. So, I’ve ported your 1.2.1 code to this regular AS3 function (not an object/class, though that would be easy to get from what I’ve done, too!).

    Since escaping all that reg-ex stuff to post here in the comments would be ridiculous, I’m going to post a URL here that can be used to retrieve a text file with the code in it.

    Steven, if want to, grab that text file and place the formatted code somewhere on this page or in this comment, that way people who come here later won’t have to go to my site to find it. 🙂

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