HTML <base> TAG and local folder path with Internet Explorer

I am trying to use < base> TAG to indicate the source folder containing the media files for my html pages located in separate folder.

I have the following folder structure:

A
|- HTML_PAGES        (contains html files)
|- MEDIA_FOLDER      (contains the media used by this html pages)

I try to indicate the 开发者_开发知识库html files with the media used by html pages - so, in each html file i have something like this:

<base href="../MEDIA_FOLDER"/>

And the problem is: it works for some browsers (Opera, Chrome) but it doesn't work for Internet Explorer and Firefox. How to make it work with IE and Firefox?

This is definitely a very annoying bug in IE, but I just found a workaround.

The thing to realize is that IE does resolve the relative path, and then promptly ignores it. You can even see the fully resolved URL by checking the value of the base tag's 'href' property later on using JavaScript. So this (rather silly) piece of code resets the <base> tag's 'href' attribute to the very full URL that IE had already resolved, thereby causing it to no longer be ignored.

Add the following HTML to the top of your page, right after the tag and before you actually use any URLs:

<!--[if IE]><script type="text/javascript">
    // Fix for IE ignoring relative base tags.
    (function() {
        var baseTag = document.getElementsByTagName('base')[0];
        baseTag.href = baseTag.href;
    })();
</script><![endif]-->

(conditional comments necessary since this code can break the <base> tag in Safari/Chrome, and other browsers clearly don't need it.)

Such a silly bug.

It looks like there are two separate issues with IE8 and IE9.

http://social.msdn.microsoft.com/Forums/en-US/iewebdevelopment/thread/c51bb8b9-40ab-437b-a125-88b660f3e1ca/

http://social.msdn.microsoft.com/Forums/en-US/iewebdevelopment/thread/e5cfdf07-494c-4703-aa4a-34a1a548de05/

A workaround that seems to be working in IE8 and IE9 is including http:// in the base href. I am not experiencing any issues in Firefox (v9)

Use an absolute URL:

<base href="http://yourdomain.com/MEDIA_FOLDER"/>

<base href="../MEDIA_FOLDER"/>

Doesn't have a trailing slash, so it refers to a file called MEDIA_FOLDER and not a folder. Often you don't notice the difference because web servers will redirect an attempt to fetch folder to the proper address folder/, which will then typically return a default document (eg. folder/index.html). But for relative URL resolution it does make a difference.

target relative to /folder is not /folder/target, it's just /target. To make it /folder/target you must let the browser know that the base URL is a folder, by adding a trailing slash:

<base href="../MEDIA_FOLDER/"/>

There is no reason for different browser behaviour here. A place you may find different browser behaviour, though, is if you've accidentally used a Windows-filesystem-style backslash \ instead of /, so do check for that.

Richard's answer got me close to the working solution, here is what I ended up adapting it to.

<!--[if IE]><script type="text/javascript">
    // Fix for IE ignoring relative base tags.
    (function() {
        var baseTag = document.getElementsByTagName('base')[0];
        baseTag.href = window.location.protocol + '//' + window.location.host + baseTag.href;
    })();
</script><![endif]-->

I'm not sure how BASE works with directory relative urls, try giving it a root relative url like

<base href="/MEDIA_FOLDER"/>

Is your base element inside the body element? That could cause the problem. (Check in Firebug, it might end up in the body even if your code looks okay on first sight.)

This is a known issue and it's that IE requires closing the tag but not Firefox, the other browsers simply don't care. Here is what works for me:

<base href="{BASE_PATH}"><!--[if IE]></base><![endif]-->

Feel free to tweak at your will, and of course replace {BASE_PATH} with your actual path, i normally use an absolute path, but i've seen this work for relative too

EDIT: And please note that your path should end with a trailing slash

I consider that people reading this are dealing with enterprise or legacy web applications.

We can't rely on the IE Conditional Comments as it just might be ignored by IE, believe it or not. At least, it is my persisting case.

I added below my script which is browser features' agnostic.

It was tested in IE11 under IE-5-7-8-9-10-11 render modes with HTML5 <!DOCTYPE html>.
With the IE Enterprise mode and without.

It works for relative paths like ../MEDIA_FOLDER/.

It works for my_child_folder/MEDIA_FOLDER/ with the exception of IE7-5.
I'm a little lazy to fix it and encourage you to use rooted paths.
I.e. simply use /some_root_folder/my_child_folder/MEDIA_FOLDER/ instead of my_child_folder/MEDIA_FOLDER/. (Or improve my script, or do not use IE7-5.)

We have two main bugs here and a bunch of cases.

First, IE9 and IE8 auto-convert a path value in the href attribute to an URL. They do this, just like all modern browsers.
But IE page doesn't see this auto-change. We just fix this by re-assining of the href baseTag.href = baseTag.href.

Second, IE7-5 do not produce auto-conversion of a path value to an URL value. We should do it manually.

There are other situations which slightly change IE behavior. This depends on

• What DOCTYPE do you use.
• How do you render you base tag - <base/>, <base></base> or <base>.
• How your IE Enterprise Mode deals with IE Compatibility View setting.

For example if you have the IE Enterprise Mode set to IE8 with the Compatibility View set on then IE will set IE7 User-Agent HTTP header and ASP.NET Forms will be rendering for IE7.
Or the IE Conditional Comments will be ignored in case of pop-ups, frames, iframes or on common pages. These are all my real cases.

(function () {
    // Fixes old IE wrong behaiors of the href attribute of the base tag.

    var preventIeHrefIgnoring = function (baseTag) {
        var docMode = document.documentMode;
        var isIe = docMode;
        if (!isIe)
            return;
        if (docMode != 8 && docMode != 9)
            return;

        // IE8 and IE9 auto-convert path-like values of the href attribute, but do not apply it on the page.
        // It is fixed by re-assining.
        baseTag.href = baseTag.href;
    }

    var baseColl = document.getElementsByTagName('base');
    if (!baseColl.length)
        return;
    var baseTag = baseColl[0];

    var initialHref = baseTag.href;
    if (!initialHref)
        return;

    var hrefIsUrl = initialHref.indexOf("https://") == 0 || initialHref.indexOf("http://") == 0;
    if (hrefIsUrl) {
        preventIeHrefIgnoring(baseTag);

        return;
    }

    // Below we are dealing with IE7-5 only.

    var targetHref = initialHref.indexOf('/') == 0 ? initialHref : "/" + initialHref;

    var resultHref = window.location.protocol + "//" + window.location.host + targetHref;
    baseTag.href = resultHref;
})();