How could I check the built-in graph title font?

Grafana
2

Do you mean the panel title?

There are two css classes for the title: panel-titleand panel-title-text.

HTML looks like this:

<div class="panel-title-container drag-handle" panel-menu="">
  <span class="panel-title drag-handle pointer">
    <span class="icon-gf panel-alert-icon"></span>
    <span class="panel-title-text drag-handle">PANEL TITLE</span>
    <span class="panel-time-info ng-hide" ng-show="ctrl.timeInfo"><i class="fa fa-clock-o"></i> </span>
  </span>
</div>

There is currently no css defined for panel-title-text but panel-title scss can be found here: