How big can a user agent string get?

http database-design http-headers user-agent
JoshBerke picture JoshBerke · Mar 17, 2009 · Viewed 92.7k times · Source

If you were going to store a user agent in a database, how large would you accomdate for?

I found this technet article which recommends keeping UA under 200. It doesn't look like this is defined in the HTTP specification at least not that I found. My UA is already 149 characters, and it seems like each version of .NET will be adding to it.

I know I can parse the string out and break it down but I'd rather not.

EDIT
Based on this Blog IE9 will be changing to send the short UA string. This is a good change.

Answer

vartec picture vartec · Mar 17, 2009

HTTP specification does not limit length of headers at all. However web-servers do limit header size they accept, throwing 413 Entity Too Large if it exceeds.

Depending on web-server and their settings these limits vary from 4KB to 64KB (total for all headers).

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