Multiple Explorers

A major web development problem used to be that it was not possible to run two or more versions on the same computer.

A solution has been found however, by web developer Joe Maddalone who deserves eternal fame. Read his page for the technical details.

Web developer Ryan Parman made the customized browsers files available on his site. I copied them to my server to make sure this valuable resource doesn't disappear. Subsequently I found similarly doctored Explorer 3 and 4 versions on

Here's how it works:

  1. Start with a Windows XP box with Explorer 6 installed on it. I have heard, but not tested, that this will also work on Windows 2000.
  2. Download the browsers of your choice:
  3. Unzip the zip files and put them somewhere in a directory.
  4. To run the browsers, execute the IEXPLORE.EXE files in each directory. This works. Nonetheless, keeping the versions apart is not simple.
  5. I verified that this were in fact working copies of 5.01 and 5.5 by some simple CSS tests you can do right here on this site. See below.
  6. Nonetheless you'll find problems. The Help -> Info screen, for instance, always shows the Explorer 6.0 version number, even though the image above it says "Explorer 4" in 4.0, "Explorer 5" in 5.0, but "Explorer 6.0" in 5.5.
  7. The user agent string seems to work fine, though. To help you keep these versions apart I wrote a simple script that precedes the document title by the IE version.


  1. The Explorer 4.0 version is not quite the same as a single-install Explorer 4. Duncan O'Neill has set up a simple test that shows a multiple-installed Explorer 4 allows certain @import statements that a single-installed Explorer 4 doesn't allow.
  2. Test Explorer 5.0 by going to the > selector page. In 5.5 and 6 nothing happens, since these two browsers do not support the > selector at all. 5.0, however, interprets my test as "make all paragraphs italic".
  3. Test Explorer 5.5 by its lack of support for the display: list-item declaration.

Explorer 4 bug

All these browsers work perfectly, with the exception of Explorer 4. Explorer 4 refuses to accept any URL you type into the location bar. Instead you should open a file by Ctrl+O and entering the URL in this box. Clicking on a link works fine.

Conditional comment bug

Another problem you must know about: when you use conditional comments the comments will be interpreted the same by all browsers. Generally this means that if you have Explorer 6.0 installed, conditional comments will pretend all Explorers on your computer are Explorer 6.0. This means that it's impossible to test conditional comments for Explorer versions below 6.0

Favourites bug

All Explorers except the original system one (usually IE 6) have serious problems with their Favourites. On my system, IE 5.0 and 5.5 crash as soon as you click on "Favourites". IE 4 doesn't, but for some odd reason it starts up the Print dialogue.

Cookies bug

Several readers reported that older Explorers don't support cookies any more in this setup. I have no idea how to solve this problem.

On Win98

My old method, maintained mainly for the record.

When you start with a clean Win98 First Edition installation with Explorer 4, you can install this full Explorer 5.01 next to it. It's a bitch to download (66 Meg), but I can guarantee that it works because I've done it.

Be sure to choose Custom Install. One one of the installation screens you see an 'Advanced' button. Click on it, and you see a screen with a checkbox 'Keep Explorer 4 in compatibility mode' or some such text. Be sure to check this checkbox, then continue the installation. It works.

Years ago I used the same trick on WinNT, and there it worked fine, too. I have heard, but not personally tested, that you can install Explorer 5.5 in a similar way. Note that you must choose between 5.0 and 5.5, though, installing both next to 4 is impossible.

It is said that Explorer 4 won't function quite the same after you've installed 5.0 or 5.5 next to it. However, I never found any problems. The source of this rumour seems to be the alert box that Explorer 4 pops up the first time you start it after having installed another version. Nonetheless all the old faithful CSS and JavaScript bugs work fine on this 'compatible' Explorer 4. Therefore I do not believe this rumour any more.