What is the default log_format on Nginx?
Solution 1:
Accoding to: https://nginx.ru/en/docs/http/ngx_http_log_module.html default log format is Combined. If the format is not specified then the predefined “combined” format is used.
Solution 2:
To expand on Alexander's answer, the definition of the default "combined" log format is given at the end of log_format section. At least for nginx 1.21 it is
log_format combined '$remote_addr - $remote_user [$time_local] '
'"$request" $status $body_bytes_sent '
'"$http_referer" "$http_user_agent"';