I am learning about cookies, and I wonder about browser support:
For each domain/web site, how many cookies may be sent to a browser, and of what size?
If multiple cookies are sent and stored, does that affect performance?
Based on my research I recommend you use no more than 50 cookies, and no more than 4093 bytes for all cookies per domain.
The lowest common denominator is:
Out of interest, notice that IE has a character limit while most have a byte limit. This means for multi-byte encodings like UTF-8 IE can fit in more data.
You can read more here: http://browsercookielimits.squawky.net/
Different browsers have different size limits on cookies. Some general guidelines:
A page that lists the actual in-practice cookie limits for several browsers:
Cookies are not saved on a server basis but on a domain basis (a server may host many domains or the opposite a server farm may be serving a single domain).
In general, I would avoid saving lots of information in cookies, as the data gets sent to and from the browser on every request. As you suggest in your question, this can have a effect on performance.
Usually one stores small amounts of data in the cookie, mostly used to identify the user/session so more data can be picked up from a database or another resource local to the web server.