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?
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it's fine where it is; we now have two versions, one for SU (browser exe info) and one for SO (programmery info) stackoverflow.com/questions/2093793/…– Jeff AtwoodJan 19, 2010 at 16:57
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2 Answers
Different browsers have different size limits on cookies. Some general guidelines:
Most of the documentation I've found (and there isn’t much) suggests that web browsers must support a minimum of:
- 300 cookies in total
- 20 cookies per domain
- 4096 bytes per cookie
It seems as though this minimum requirement is part of the original RFC for cookies – see section 6.3 specifically.
A page that lists the actual in-practice cookie limits for several browsers:
Per Domain Cookie Limit
Here is a test script to test your browser:
- Firefox 2: 501
- Firefox 3: 501
- Internet Explorer 72: 50 (after applying a patch from Microsoft)
- Opera 9: 30
- Safari: No Limit(!)
Maximum Cookie Limit:
- Firefox 2: 10001
- Firefox 3: 10001
- Internet Explorer: unknown
- Opera: unknown
1 can be set between 0 and 65535
2 documented by Microsoft here
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.
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Cookies are quite unreliable as a state-preserving tool, because browser settings may block cookies from some or all domains.– harrymcJan 19, 2010 at 17:21
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Here is a test page containing many of the latest browser limits. Some have moved on since this was written.– IainApr 9, 2011 at 21:16
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:
- IE 8/9/10/11 have a limit of 50 cookies, 5117 characters per cookie, and 10234 bytes per domain
- Safari ?? on iPad iOS 5.1 have a limit of 600 cookies, 4093 bytes per cookie, and 4093 bytes per domain
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/
