Measuring impressions with OMID

Media Owners
Last Updated: April 30, 2026•

Index Exchange (Index) uses the IABClosed Interactive Advertising Bureau (IAB). An advertising business organization that develops industry standards, conducts research, and provides legal support for the online advertising industry.'s Open Measurement Interface Definition (OMID) to measure impressions for mobile app banners. OMID allows billing notifications to be sent to Index and DSPs when at least one pixel of an ad enters the user’s viewport. We encourage all mobile app Media Owners to adopt OMID because it standardizes the measurement of impressions and reduces reporting discrepancies between all parties. To start using OMID with Index, send API = 7 in the Banner object of your OpenRTB bid requests.

In the mobile app banner example below, the following steps describe how OMID works in an OpenRTBClosed An open industry standard for communication between buyers and sellers of online advertising in real-time bidding auctions. It's published by the IAB. interaction between a publisherClosed The owner of a website or app where advertisements are served., Index, and a DSPClosed Demand-Side Platform (DSP). A software platform that automates bidding decisions in real-time and efficiently connects buyers and audiences through an ad exchange or SSP. Also known as a buy-side platform..

Diagram showing how OMID works

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The ad SDK generates an ad request and sends it to your ad serverClosed A platform that manages, stores, and delivers advertisements to a publisher's site.. The ad server then makes a bid requestClosed An OpenRTB request that is sent from a supply-side platform (SSP) or ad exchange to the DSP requesting a bid response for potential impressions. A bid request contains information about the impression that allows the DSP to decide whether to bid on the impression. to Index.

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Index sends a bid request to the DSP.

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The DSP sends a bid responseClosed An OpenRTB response that is sent by the DSP in response to the SSP's or ad exchange's bid request. It is an event directed back to the seller expressing a valuation for the request and conditions of sale. to Index that includes the following fields in the bid response object:

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Index injects our OMID measurement script into the adm field of the bid response object.

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Index sends a bid response to your ad server that includes the Index OMID script.

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Your ad server conducts the final auction and if the bid wins the auction, the ad is displayed to the user.

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When at least one pixel of the ad enters the viewport of the device, Index's OMID script determines that a billable event has occurred and fires both the Index impression notification and the DSP burl simultaneously.

Note: Index uses a time to live (TTL) of three hours for our impression notifications. Our impression notification, as well as the DSP’s, are fired when the OMID measurement script runs, regardless of the DSP’s TTL for impression notifications. Index recommends against pre-rendering creatives in order to reduce discrepancies with all parties. For more information about TTL, see How Index counts impressions.