full page caching problem with built-in cache magento2

[dimitri_karras]

I am running Magento 2.2.3, apache 2.4, and have it set in the settings to use the built-in cache system. Varnish is not installed.

Full page cache is activated. There are no blocks which are set to not cacheable. 

When I check the site headers i get: 

Pragma no cache

Cache-Control max-age=0, must-revalidate, no-cache, no-store 

additionally, when I go to the settings and switch from built-in to Varnish (despite varnish not existing on the server), i get correct cache-control headers. 

any ideas on what could be causing this issue?

[JLHC]

I don't believe that the full page cache will work if you are not using Varnish. 

The built-in cache system is just the file cached that are located in /var/caches. If you see cache files populated under the directory, it means that cache is working. 

[dan_sanderson]

What you are looking at there is the headers set for browser client side caching instructions.

"Pragma no cache

Cache-Control max-age=0, must-revalidate, no-cache, no-store"

Switch your Magento environment to developer mode and you should be looking for 

• X-Magento-Cache-Debug: HIT
• X-Magento-Cache-Debug: MISS

On first page load you will encounter a miss as the cache gets warmed.

On second page load you should see the X-Magento-Cache-Debug: HIT headers

[Janusz_Sprii]

Full page cache works without varnish