Default nginx client_max_body_size

The default value for client_max_body_size directive is 1 MiB.

It can be set in http, server and location context — as in the most cases,
this directive in a nested block takes precedence over the same directive in the ancestors blocks.

Excerpt from the ngx_http_core_module documentation:

Syntax:   client_max_body_size size;
Default:  client_max_body_size 1m;
Context:  http, server, location

Sets the maximum allowed size of the client request body, specified in
the “Content-Length” request header field. If the size in a request
exceeds the configured value, the 413 (Request Entity Too Large) error
is returned to the client. Please be aware that browsers cannot
correctly display this error. Setting size to 0 disables checking of
client request body size.

Don’t forget to reload configuration
by nginx -s reload or service nginx reload commands prepending with sudo (if any).