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What Is the Difference Between Flex and Fixed Size Ad Slot?

Learn more about Flex and Fixed-size ad slots here


All Social Display creatives are trafficked and tracked in your DSP as display tags. 

Nova ad tags are targeted to IAB standard display sizes (300x250, 300x600, 320x480 and 336x280). 

Flex (Full Sized) Ad Slot

  • Nova social display ads are responsive
  • The ads will be rendered as flex (full-sized) size by default and automatically resize the ad slot's iframe.
  • If trafficked to a standard 300x250, 300x600, 320x480 and 336x280 ad slot, the slot automatically resizes and loads the Flex size
  • As a result, they appear much larger than the standard display ad size and deliver better creative performance when Flex size is used.
  • Nova tag dynamically checks to see if the ad slot is non-resizable. If so, it falls back to its fixed-sized version
  • A separate tag does not need to be trafficked as this happens automatically

Caution: There could be an instance where our ad tag is resizing as Flex but the Parent DIV (HTML Element) is not letting the ad resize and cutting the ad preview, in such a case, you should Blacklist such domain.

  • We recommend the following exchanges for optimizing for Flexible Inventory:
    • Pubmatic
    • OpenX
    • Index  Exchange
    • AppNexus
    • Magnite
    • Bidswitch.

      There are certainly more and other exchanges you can use, these have simply been reported as the best performing!

Note: The reason you see the 300x250, 300x600, 320x480 and/or  336x280 previews in our dashboard is to ensure that you are able to see how the ad will render in case it hits a site that does not allow resizing and loads our fixed-size


All social display creatives will automatically render the fixed-size fallback template when served to un-resizable ad slots of that size.


Fixed Ad Slot

  • These ads remain a specific size (like 300x250, 300x600, 320x480 or 336x280) and do not resize automatically
  • About 10% of sites in the open web load ads in Safe-frames

There are 3 instances where fixed-sized ads automatically load

  1. When the ad is trafficked to safe-frames, e.g. GAM SSP (Google Adx supply).

  2. When the ad is trafficked to App inventory

  3. When the ad lands on an AMP site (very rare).


In general, to reduce fixed-sized rendering percentage and ensure good performance we recommend blacklisting the following domains:

Rendering options

  1. Flex
  2. Fixed 300x250
  3. Fixed 336x280
  4. Fixed 300x600
  5. Fixed 320x480


Read more about Nova Rendering Options


Have any questions or facing any issues? Send us your request at support@createwithnova.com