May 26, 2018

Parser for the User Agent string

ParseHTTPUserAgent implements a rules-based parser and tries to identify MSIE, FireFox, Opera, Safari & Chrome first. It then tries to identify Mozilla, Netscape, Robots and the rest will be tried with a generic parser. There is also a structure dumper, useful for debugging.

User agent strings are a complete mess since there is no standard format for them. They can be in various formats and can include more or less information depending on the vendor’s or the user’s choice. Also, it is not dependable since it is some arbitrary identification string. Any user agent can fake another. So, why deal with such a useless mess? You may want to see the choice of your visitors and can get some reliable data even if some are fake and generate some nice charts out of them or just want to send an HttpOnly cookie if the user agent seems to support it and send a normal one if this is not the case. However, browser sniffing for client-side coding is considered a bad habit.

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