clientmaxbodysize

client_max_body_size is an Nginx directive that sets the maximum size of the client request body that Nginx will process. It can be placed in the http, server, or location context, allowing limits to be applied globally or scoped to specific servers or paths. The default value is 1m (one megabyte).

The value is a size specification that supports units with suffixes K, M, or G (case-insensitive). For example, 2m sets a two-megabyte limit, and 10m sets a ten-megabyte limit. A value of 0 disables the limit, effectively allowing any request body size, subject to available resources and other constraints.

If an incoming request body exceeds the configured limit, Nginx responds with the HTTP 413 Request Entity Too Large status and does not pass the request to the upstream server. This directive mainly affects file uploads and large payloads sent via POST, PUT, or PATCH, and interacts with other body-related settings such as client_body_buffer_size and client_body_timeout.

Configuration typically involves placing the directive in the http block for a global limit, or within a server or location block to override the global setting for particular hosts or paths. Nested blocks with more specific contexts take precedence over broader ones.

Usage notes: set a value appropriate for expected upload sizes and available server resources. Higher limits can increase memory usage during body buffering; lower limits can prevent large, potentially abusive uploads. When using reverse proxies or application backends, ensure that downstream components also enforce suitable limits to avoid inconsistencies.