How Index counts impressions

DSPs
Last Updated: February 17, 2026•

When a DSP wins an auction, Index Exchange (Index) stores the billing notification URL (burl), which is to be sent when a billable event has occurred. Based on the ad format, Index counts a billable event and sends the DSP burl when the billing notification from the Media Owner meets the following criteria:

Format Impression counting criteria

Web banner

Index expects to receive the billing notification in the adm field within the time to live (TTL) of 600 seconds.

Note: You will receive the billing notification from Index as soon as we receive it from the Media Owner, up to the TTL.

Mobile app banner

  • If you use burl:

  • And the Media Owner supports OMID, Index will send our impression notification and your burl at the same time, when at least one pixel of the banner is painted into the device's viewport.

  • And the Media Owner does not support OMID, but does support burl, both you and Index will receive burl-based impression notifications at the same time.

  • And the Media Owner does not support OMID or burl, your burl will be placed in the adm, and both you and Index will receive burl-based impression notification.

  • If you do not use burl, Index assumes that your impression tracking URL is in the ad markup (adm) that you return. We will still attempt to use OMID or burl for impression counting with Media Owners that support it.

Note: Index uses a TTL of 600 seconds for adm-based impression notifications from Media Owners, and a TTL of three hours for OMID and burl-based impression notifications.

Video (instream and outstream) on web, mobile app, and STV

Index expects to receive the billing notification from our VAST adm within the TTL of:

  • One hour for video (instream and outstream) on web.

  • Three hours for mobile app and STV.

Note: You will receive the billing notification from Index as soon as we receive it from the Media Owner, up to the TTL.

Native on web and mobile app

Index expects to receive the billing notification in the imptrackers[] array or eventtrackers[] array in the native adm within the TTL of 300 seconds.

Note: You will receive the billing notification from Index as soon as we receive it from the Media Owner, up to the TTL.

Index does not count impressions in the following situations:

  • When billing notifications don't pass our invalid traffic (IVT) standards. Index uses industry-standard IP address and UserAgent blocklists, as well as proprietary methods and data sets to filter invalid traffic.

  • When the same billing notification is sent twice within a given TTL, the second notification will be discarded as a duplicate.

  • When Index is previewing or testing creatives for ad quality, no impressions will be counted.

  • When billing notifications are sent after Index's TTL timeout value.