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Increasing max file upload size


By default, file uploads are restricted to less than 32 MB, on a server-by-server basis, to prevent abuse by unauthorized activity. If you need a larger allowance, a few variables are necessary to tune.


Allowing larger file uploads consists of three tunable variables. These variables may be tuned either through an .htaccess or ini_set. For simplicity, the following example will assume adjustment in a .htaccess file.

Only upload_max_filesize, post_max_size, and memory_limit are relevant tunable parameters. max_execution_time and max_input_time do not affect uploads.

upload_max_filesize: controls the maximum file upload size permitted in a form. This can be suffixed with “m” to denote a size in megabytes, e.g. php_value upload_max_filesize 32m

post_max_size: a sum of all parameters submitted by a form. As a general rule: this should be approximately 33% more than upload_max_filesize, e.g. php_value most_max_size 42m

Explanation: all submitted file uploads are transcoded to base64, which results in approximately a 33% increase in actual consumption (over initial input). Therefore, simply, if an upload is 6 MB, anticipate an actual input of ~ 9 MB. This value must be higher than upload_max_filesize because there are control variables that dictate the file upload constraints (session variables) that must be included in transmission. post_max_size must accommodate upload_max_filesize x 33% + input vars, which typically occupy only a few hundred kilobytes.

memory_limit: this is a non-tunable parameter, without justification,  By default, limits are set to 96 MB on pre-v6 platforms and 192 MB on v6+ platforms. memory_limit affects the amount of memory a PHP script may occupy, in addition to file buffers that may be loaded into memory (think file_get_contents swallowing a file; fread would only buffer up to n bytes so long as temporary variable storage is recycled in an iterative loop!). Depending upon implementation, memory_limit may have no impact on file uploads. It succinctly boils down to the maxim of “don’t do bad things”; don’t write crappy code!

If you are at the mercy of crappy code, open a ticket for us within the control panel to take a look at it and determine a reasonable course of action. We’ll perform an appraisal of your situation, and in most situations, raise your memory limit.


Updated on July 8, 2019

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