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What is the maximum length of a URL in different browsers?


Question

What is the maximum length of a URL in different browsers? Does it differ among browsers?

Does the HTTP protocol dictate it?

2018/09/18
1
4931
9/18/2018 5:24:41 PM

Accepted Answer

Short answer - de facto limit of 2000 characters

If you keep URLs under 2000 characters, they'll work in virtually any combination of client and server software.

If you are targeting particular browsers, see below for more details specific limits.

Longer answer - first, the standards...

RFC 2616 (Hypertext Transfer Protocol HTTP/1.1) section 3.2.1 says

The HTTP protocol does not place any a priori limit on the length of a URI. Servers MUST be able to handle the URI of any resource they serve, and SHOULD be able to handle URIs of unbounded length if they provide GET-based forms that could generate such URIs. A server SHOULD return 414 (Request-URI Too Long) status if a URI is longer than the server can handle (see section 10.4.15).

That RFC has been obsoleted by RFC7230 which is a refresh of the HTTP/1.1 specification. It contains similar language, but also goes on to suggest this:

Various ad hoc limitations on request-line length are found in practice. It is RECOMMENDED that all HTTP senders and recipients support, at a minimum, request-line lengths of 8000 octets.

...and the reality

That's what the standards say. For the reality, there was an article on boutell.com (link goes to Internet Archive backup) that discussed what individual browser and server implementations will support. The executive summary is:

Extremely long URLs are usually a mistake. URLs over 2,000 characters will not work in the most popular web browsers. Don't use them if you intend your site to work for the majority of Internet users.

(Note: this is a quote from an article written in 2006, but in 2015 IE's declining usage means that longer URLs do work for the majority. However, IE still has the limitation...)

Internet Explorer's limitations...

IE8's maximum URL length is 2083 chars, and it seems IE9 has a similar limit.

I've tested IE10 and the address bar will only accept 2083 chars. You can click a URL which is longer than this, but the address bar will still only show 2083 characters of this link.

There's a nice writeup on the IE Internals blog which goes into some of the background to this.

There are mixed reports IE11 supports longer URLs - see comments below. Given some people report issues, the general advice still stands.

Search engines like URLs < 2048 chars...

Be aware that the sitemaps protocol, which allows a site to inform search engines about available pages, has a limit of 2048 characters in a URL. If you intend to use sitemaps, a limit has been decided for you! (see Calin-Andrei Burloiu's answer below)

There's also some research from 2010 into the maximum URL length that search engines will crawl and index. They found the limit was 2047 chars, which appears allied to the sitemap protocol spec. However, they also found the Google SERP tool wouldn't cope with URLs longer than 1855 chars.

CDNs have limits

CDNs also impose limits on URI length, and will return a 414 Too long request when these limits are reached, for example:

(credit to timrs2998 for providing that info in the comments)

Additional browser roundup

I tested the following against an Apache 2.4 server configured with a very large LimitRequestLine and LimitRequestFieldSize.

Browser     Address bar   document.location
                          or anchor tag
------------------------------------------
Chrome          32779           >64k
Android          8192           >64k
Firefox          >64k           >64k
Safari           >64k           >64k
IE11             2047           5120
Edge 16          2047          10240

See also this answer from Matas Vaitkevicius below.

Is this information up to date?

This is a popular question, and as the original research is ~14 years old I'll try to keep it up to date: As of Sep 2020, the advice still stands. Even though IE11 may possibly accept longer URLs, the ubiquity of older IE installations plus the search engine limitations mean staying under 2000 chars is the best general policy.

2020/09/01
5053
9/1/2020 1:29:53 PM

The longest URLs I came across are data URLs

Example image URL from Google image results (11747 characters)

data:image/jpeg;base64,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
2012/11/29

WWW FAQs: What is the maximum length of a URL? has its own answer based on empirical testing and research. The short answer is that going over 2048 characters makes Internet Explorer unhappy and thus this is the limit you should use. See the page for a long answer.

2019/12/13

I wrote this test that keeps on adding 'a' to parameter until the browser fails

C# part:

[AcceptVerbs(HttpVerbs.Get)]
public ActionResult ParamTest(string x)
{
    ViewBag.TestLength = 0;
    if (!string.IsNullOrEmpty(x))
    {
        System.IO.File.WriteAllLines("c:/result.txt",
                       new[] {Request.UserAgent, x.Length.ToString()});
        ViewBag.TestLength = x.Length + 1;
    }

    return View();
}

View:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

<script type="text/javascript">
    $(function() {
        var text = "a";
        for (var i = 0; i < parseInt(@ViewBag.TestLength)-1; i++) {
            text += "a";
        }

        document.location.href = "http://localhost:50766/Home/ParamTest?x=" + text;
    });
</script>

PART 1

On Chrome I got:

Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36
2046

It then blew up with:

HTTP Error 404.15 - Not Found The request filtering module is configured to deny a request where the query string is too long.

Same on Internet Explorer 8 and Firefox

Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)
2046

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Firefox/38.0
2046

PART 2

I went easy mode and added additional limits to IISExpress applicationhost.config and web.config setting maxQueryStringLength="32768".

Chrome failed with message 'Bad Request - Request Too Long

HTTP Error 400. The size of the request headers is too long.

after 7744 characters.

Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36
7744

PART 3

Added

<headerLimits>
    <add header="Content-type" sizeLimit="32768" />
</headerLimits>

which didn't help at all. I finally decided to use fiddler to remove the referrer from header.

static function OnBeforeRequest(oSession: Session) {
    if (oSession.url.Contains("localhost:50766")) {
        oSession.RequestHeaders.Remove("Referer");
    }

Which did nicely.

Chrome: got to 15613 characters. (I guess it's a 16K limit for IIS)

And it failed again with:

<BODY><h2>Bad Request - Request Too Long</h2>
<hr><p>HTTP Error 400. The size of the request headers is too long.</p>


Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36
15613

Firefox:

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Firefox/38.0
15708

Internet Explorer 8 failed with iexplore.exe crashing.

Enter image description here

After 2505

Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)
2505

Android Emulator

Mozilla/5.0 (Linux; Android 5.1; Android SDK built for x86 Build/LKY45) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/39.0.0.0 Mobile Safari/537.36
7377

Internet Explorer 11

Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C)
4043

Internet Explorer 10

Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/6.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C)
4043

Internet Explorer 9

Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
4043
2018/08/23

There is really no universal maximum URL length. The max length is determined only by what the client browser chooses to support, which varies widely. The 2,083 limit is only present in Internet Explorer (all versions up to 7.0). The max length in Firefox and Safari seems to be unlimited, although instability occurs with URLs reaching around 65,000 characters. Opera seems to have no max URL length whatsoever, and doesn't suffer instability at extremely long lengths.


On Apple platforms (iOS/macOS/tvOS/watchOS), the limit may be a 2 GB long URL scheme, as seen by this comment in the source code of Swift:

// Make sure the URL string isn't too long.
// We're limiting it to 2GB for backwards compatibility with 32-bit executables using NS/CFURL
if ( (urlStringLength > 0) && (urlStringLength <= INT_MAX) )
{
...

On iOS, I've tested and confirmed that even a 300+ MB long URL is accepted. You can try such a long URL like this in Objective-C:

NSString *path = [@"a:" stringByPaddingToLength:314572800 withString:@"a" startingAtIndex:0];
NSString *js = [NSString stringWithFormat:@"window.location.href = \"%@\";", path];
[self.webView stringByEvaluatingJavaScriptFromString:js];

And catch if it succeed with:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    NSLog(@"length: %@", @(request.URL.absoluteString.length));
    return YES;
}
2019/04/11

Source: https://stackoverflow.com/questions/417142
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