Browser Cookie Limits

I have a requirement to store a large amount of data in cookies, to figure out if it will work here are my tests.

If all you care about is the conclusion, well here it is: If you want to support most browsers, then don't exceed 50 cookies per domain, and don't exceed 4093 bytes per domain (i.e. total size of all cookies <= 4093 bytes)

Your Browser Test Results

About The Tests

Max Cookie Count Per Domain is calculated by adding cookies until the number of cookies saved stops increasing.

Max Cookie Size Per Cookie is calculated by increasing the cookies value one character at a time, until the saved value is truncated.

Max Cookie Size Per Domain is guessed by adding cookies of maximum size, until no more cookies can be added. Hence, the actual limit may be more than the guessed limit. Guessed Limit <= Actual Limit < Guessed Limit + Max CookieSize

Manually Execute Tests

1. Max Cookies Test

Each cookie will be filled with the following character, repeated the specified number of times.
Character: Repeat Character Times:

Some Interesting Things

Typically, the following are allowed: * Given 20 cookies of max size 4096 = 81920 bytes.

IE (and Opera) introduces a new limit, max bytes per domain

A few notes about cookies:


Limits Per Browser

After testing a few browsers myself, and using Browser Shots I have compiled the following list:
Browser Max Cookies Max Size Per Cookie Max Size Per Domain1 Usage2
Chrome 4
Chrome 5-7704096 bytesNA
Chrome 8-58*1804096 bytesNA60.1%
* Checked on 8/10/12/13/14/15/17/25/39/58
Chrome MobileAppears same as Chrome. Verified on Chrome Mobile 39.
FireFox 2/3.6.6504097 charactersNA
FireFox 3.6.13-19*1504097 charactersNA1.7% (assuming, versions before 25)
* verified on 3.6.13/4/8/9/10/14/19. unverified 5-8/11-13/15-18, just assumed
FireFox 21-52*1504097 bytesNA21.7%
* verified on 21/24/25/30/34/52
IE 6 unpatched204096 characters4096 characters
IE 6504096 characters4096 characters
IE 7 unpatched204095 characters4095 characters
IE 7504095 characters4095 characters0.3%
IE 8/9/10/11/15505117 characters10234 characters9.5%
Opera 8/9/10304096 bytes4096 bytes
Opera 11604096 bytes4096 bytes
Opera 12605117 bytes12093 bytes
Opera 250.6%
Opera 26/461804096 bytesN/A0.2%
Safari 3
Safari 40.1%
Safari 56004096 bytes4096 bytes
Safari 60.3%
Safari 7N/A4097 bytes8180 bytes1.4%
Safari 81.8%
Safari ? on mac360044093 bytes4most likely 4093 bytes4
Android 2.1/2.3.4504096 bytesNA
Safari Mobile 5.160054093 bytes54093 bytes
Safari Mobile 7Appears same as Safari. Verified on Safari Mobile 7.
1 NA means there is no limit other than Max Cookies * Max Size Per Cookie
2 From January 2015 W3 Schools Browser Statistics
3 Lu pointed out Safari on mac is different to windows. It appears to have no limit. I will investigate when I get more time.
4 Deeman has shared these Safari Mac results in the comments below.
5 Safari on my iPad 3 iOS 5.1 has a limit of 4096 bytes, but an overhead of 3 bytes per cookie. Hence the max for 1 cookie is 4093, and I can fit 512 cookie of 5 bytes as 512*(5+3)=4096.


If you want to support most browsers, then don't exceed 50 cookies per domain, and don't exceed 4093** bytes per domain (i.e. total size of all cookies <= 4093 bytes).

** I previously said 4095 bytes to account for IE7, but now iPad 3 appears to come in a little lower.

By Iain Roberts. Created 02 March 2011. Last Updated 05 March 2013.


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