title: When does DFP record impression?
body: <p>Does DFP record an impression when ad is visible to the user or when ad is rendered?</p>
  
  <p>I'd like to record impression myself and wonder when I should record it.</p>
  
  <p>Below are the two closest point where I could record impression.</p>
  
  <p>ImpressionViewableEvent (<a href="https://developers.google.com/doubleclick-gpt/reference#googletageventsimpressionviewableevent" rel="nofollow">https://developers.google.com/doubleclick-gpt/reference#googletageventsimpressionviewableevent</a>)</p>
  
  <p>SlotRenderEndedEvent (<a href="https://developers.google.com/doubleclick-gpt/reference#googletageventsslotrenderendedevent" rel="nofollow">https://developers.google.com/doubleclick-gpt/reference#googletageventsslotrenderendedevent</a>)</p>