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On browsers, it varies and we can see this be searching for max cookie size. But referencing http://browsercookielimits.squawky.net/ developers should not go beyond 4097 4KB per domain and the safer number should be 2KB.
Cookies are also involved here as they are transmitted within request header.
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Note: Servers ought to be cautious about depending on URI lengths |
Errors
If the limit is exceeded the following can occur,
Server tuncates or responds with an HTTP 414 error.
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References
Good response on maximum http request - https://stackoverflow.com/questions/2659952/maximum-length-of-http-get-request
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