Interstitial Ads

An interstitial ad is a type of ad placed on mobile devices that covers the entire device screen and can be dismissed by the user. You can identify an interstitial ad opportunity in the bid request by verifying that the Google protocol's field is set to true. For OpenRTB, the BidRequest.imp[].instl field will be set to true if represented in Protobuf and 1 if the bid request is JSON.

A list of recommended standard ad sizes based on the width and height of the ad slot is passed in the bid request, The device's screen width and height are passed in the BidRequest.device message of the bid request for both the Google and OpenRTB protocols.

Sample bid requests



OpenRTB Protobuf

Buyers are free to bid with any creatives whose sizes are smaller than or equal to the screen width and height, but larger than or equal to 50% of the screen width and 40% of the screen height. Creatives aren't restricted to the recommended sizes in the ad slot; though, all recommended sizes in the bid request are guaranteed to be within the acceptable size range.

Best practices

  • Buyers should include formatting attributes in their HTML creative snippets to center the ads within the ad slot; otherwise, ads will render on the top left of the ad slot, creating a poor user experience.
  • Buyers should respond with an interstitial ad that takes up as much space as possible within the ad unit. A 1024x768 interstitial unit filled with a much smaller ad size (e.g., 320x50) should be avoided.
  • An interstitial ad should cover the entire device screen and should allow itself to be closed:
    • A user can click the X button, added automatically by our SDK, at the upper right corner to close an interstitial ad. (The publisher cannot auto-close an interstitial ad.)
    • MRAID provides an API to close an interstitial ad.
  • Buyers may receive multiple recommended sizes for an interstitial ad in the bid request. They can use these sizes to inform their bidding logic of the range of acceptable ad sizes that can be sent in the bid response.
    • Buyers are free to bid with ad sizes smaller than or equal to the screen dimensions, but larger than or equal to 50% of the screen width and 40% of the screen height. Buyers whose bidder doesn't support multiple ad slot sizes in bid requests will only be sent one size (actual screen dimensions) in bid requests.
    • If the ad size is too big or too small, the bid response is filtered with the rejection reason set to INTERSTITIAL_SIZE_MISMATCH.
    • If a buyer does not specify the ad size in response to an interstitial request, the response is filtered with the rejection reason set to MISSING_AD_SIZE.
    • Multiple width/height pairs are passed in the bid request, however the first width/height pair is always identical to the screen size.
  • Buyers should read the screen_orientation signal and respond with the appropriate creative based on what the signal returns.
    • On iOS, if the user holds the phone vertically when the request is made, but then rotates it to be horizontal before the ad returns, the ad is shown with black bars on the sides.
    • It is recommended that buyers use two creatives—one portrait and one landscape—and bid with the appropriate one based on the signal.
  • If an app publisher does not allow interstitial video ads (for example, if they support display-only interstitials), the SDK will automatically add a close (X) button regardless of the use of MRAID useCustomClose().

Sizeless / fluid interstitials

Many bidders use "fluid" (frequently referred to as "responsive" or "sizeless") interstitials that dynamically resize to take up the entire screen width and height. To ensure your creative is not re-reviewed for each individual screen size, we recommend the following:

Bid response

  • Declare the SIZELESS_ADX creative attribute (attribute 105) in your bid response.
  • BidResponse.Ad.width and BidResponse.Ad.height must still be populated with the size at which you would like the creative to render (for example, 360x480 for a 360x480 screen size).
  • Your declared width and height must still be smaller than or equal to the screen dimensions, but larger than or equal to 50% of the screen width and 40% of the screen height on each individual response.
  • Note that Authorized Buyers will not actually resize the creative; it's up to the bidder to supply a creative that dynamically resizes.

Creative pre-approval

  • When inserting a creative for pre-approval, include the SIZELESS_ADX attribute in the attribute field.
  • While the ad can serve at multiple sizes, submit the creative using a size at which you expect it to serve, that is, a common size for interstitial creatives.
  • A "sizeless" creative counts only once against your creative limit, not one for each size.


What are sizeless interstitials?
"Sizeless interstitials" are interstitial ads that automatically resize to fit the screen on which they're served. They're frequently referred to as "fluid" or "responsive."
What is changing with the sizeless interstitials launch on Authorized Buyers?
If buyers declare a creative as "sizeless" in the bid response, two things will change:
  1. Buyers will no longer need to submit creatives for each size that the ad could be (i.e., each screen size that it serves on). Only one creative review is needed and once approved the ad can then run on any screen size.
  2. There is a limit to the number of creatives a buyer can submit for approval. The sizeless interstitial creative will only count once against that limit, rather than once for each size.
Should buyers update all their creatives to be sizeless?
No—not all at once. If a creative is updated to be "sizeless" then it will need to be reapproved, so it's not recommended to update all creatives at the same time. After testing the sizeless attribute on some new creatives, the suggested approach is either:
  • Only apply it to newly added creatives moving forward.
  • Gradually add it to existing ones, and preferably under a new Buyer Creative ID.