How do I check the content of variables passed to a template file? I enabled Twig debug and I tried to debug some custom fields. However, if I try this with debug() or kint(), my application always crashes. My PHP memory size is currently 512MB; I assume that should be enough.

I realise that node is a bit too much to debug, so I tried debugging a field as in node.field_video, but that didn't work out as well.

How do I check the content of variables passed to a template file?
You can follow document. 


  To dump only the available variable keys use:


{{ dump(_context|keys) }}


In this case you can use:

{{ kint(node|keys) }}


Or you can follow topic


  Create a /modules/contrib/devel/kint/kint/config.php file and add /
  modify the line $_kintSettings['maxLevels'] = 3; (by @mdrummond on
  Slack)


The best way: install module twig_tweak and using twig function

{{drupal_dump(node)}} to dump variables.