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Internet Explorer 5.0 and higher

Microsoft released the next version of IE, 5.0, in 1999. As expected, the user-agent string once again pre-

sented problems. For example, IE 5.0 running on Windows NT 4.0 returned this user-agent string:

Mozilla/4.0 (compatible; MSIE 5.0; Windows NT)

Once again, the IE version was updated, but the Mozilla version was left at 4.0.

This pattern continued as versions 5.5 and 6.0 were released, ultimately leading to a 6.0 user-agent string

similar to this:

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT)

Because of this, it’s still necessary to do a separate check for IE.

Mozilla

As part of the development of Netscape 6 (Mozilla), a short document was written up as a specification

for the user-agent string. The new format represented the first departure from Netscape’s original user-

agent string format:

Mozilla/

MozillaVersion

(

Platform

;

Security

;

OS-or-CPU

;

Localization information

;

PrereleaseVersion] *[

;

Optional Other Comments]

) Gecko/

GeckoVersion

[ApplicationProduct/ApplicationProductVersion]

Obviously, a lot of thought went into the user-agent string format. The individual pieces of the user-

agent string are listed in the following table.

String

Required? Description

MozillaVersion

Yes

The version of Mozilla

Platform

Yes

The type of computer system being used. Possible val-

ues: Windows, Macintosh, X11 (for Unix).

Security

Yes

The security of the browser. Possible values: N (for no

security), U (for strong security), I (for weak security).

OS-or-CPU

Yes

Either the operating system the browser is being run

on or the processor type of the computer running the

browser. If the

Platform

is Windows, this is the version

of Windows (such as WinNT, Win95, and so on). If the

Platform

is Macintosh, then this is the CPU (either 68k

or PPC for PowerPC). If the

Platform

is X11, this is the

Unix operating system name as obtained by the Unix

command uname -sm.

Localization information

Yes

The language for the browser. Typically en-US in

America.

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