Detecting Browsers in Python

Dave Brueck dave at
Tue Nov 18 18:03:28 CET 2003

> Does anyone know of a simple way to have a Python script find out what
> browser is accessing it? After a web search the only thing I found to
> do this is Zope, but the system I'm programming doesn't use Zope and
> I'm not really interested in installing it just for this minor detail.
> Is there another way?

(I assume you mean that the script the browser is accessing is a CGI script)

Most browsers include a "User-Agent" in the HTTP request they make to a server.
Users can override these, but few people do, so you can semi-reliably detect
the browser that way.

I sometimes need to make sure a browser is running on "new enough" Windows, so
I use this:

ua = ua.lower()

if ua.find('win') != -1 and ua.find('win16') == -1 and \
     ua.find('windows nt 4') == -1 and ua.find('winnt4') == -1:
     # platform is Windows
     # non-Windows or old Windows

As for browser vendor, this is the pseudocode I use:

if ua.find('opera') != -1:
  # opera
elif ua.find('gecko') != -1:
  # gecko (moz/ns)
elif ua.find('msie') != -1:
  # Most likely really is IE
  # somebody else

This works for what I need because usually I'm just trying to acertain if the
browser is IE on a newer Windows box, but you may need additional checks
(Google can turn up huge lists of all known default User-Agent strings so it's
fairly easy to come up with a good test suite).


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