What does `expires -1` mean in NGINX `location` directive?

According to nginx manual, this directive adds the Expires and Cache-Control HTTP header to the response.

Value -1 means these headers are set as:

Expires: current time minus 1 second

Cache-Control: no-cache

So in summary it instructs the browser not to cache the document.

If expires -1 is used, it means that these pages are never cached. The expire directive instructs the browser to expire file cache after a certain amount of time (or at a certain time). If a negative value is given, there is no caching.