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What really happens when cookies file exceeds maximum size?

Prady
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    var i = 0; while( true ) { i++; document.cookie = i + "=" + i + ";" + document.cookie; } Try it out. – Stefan Kendall Oct 20 '09 at 16:35
  • worth pointing out that the above comment will result in an infinite loop, since browsers tend to discard old cookies when there are more than 20-ish of them for the same domain... also, it does not answer the question of a maximum file size, only maximum number of cookie files per domain – Zathrus Writer Nov 23 '17 at 13:58

3 Answers3

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The typical behavior of most browsers, to my knowledge, is to simply truncate the oldest data that does not fit.

For example, create cookies 1 through 9. When creating cookie 10 and the data size is going to overflow, cookie 1 is simply discarded.

In general practice, if you are worried about bumping into the limit and loosing cookies to overflow, it is probably time to rethink your strategy of what you are storing and start caching the data server-side and limiting the cookie to a value to access the cached data.

Mike Clark
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The file is truncated to the maximum length.

Deepakmahajan
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I think that would be browser dependent, since RFC2965 does not define a maximum size for cookies or any standard behavior for when the maximum is exceeded.

Eric Petroelje
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