Load Tracking


1. What is load tracking?

  • MoPub has introduced a new extension field in the bid response called loadtrackers that offers bidders greater visibility into the the ad delivery lifecycle – the ability to measure when an ad has been successfully loaded onto the device.

Please be advised that all MoPub Marketplace inventory requires fully secure creatives, as specified by the bidrequest.imp.secure=1 field. Further details on secure creative here.

  • Important note: This feature is OPTIONAL. MoPub is not requiring bidders build support for loadtrackers.

  • The loadtrackers field is an array of tracking URL’s that MoPub will dispatch when an ad has been successfully loaded/pre-cached on the device, before an impression has been shown. (A successful ‘load’ will not necessarily have a corresponding impression.)

Load Trackers

2. Why was this built?

  • Support for loadtrackers was added in order to increase transparency in the exchange by tracking all points of an impression, from request to load to show (impression). This helps both internal and external analysis and troubleshooting.

3. What is the benefit for buyers?

  • Funnel Visibility - This tracking ability and visibility into the ad lifecycle will allow buyers to compare the relative drop-offs from win-to-load (suggesting technical issues) and from load-to-show (suggesting a user not reaching an ad experience). A tracker submitted as part of loadtrackers should also align closely with any other trackers that are despatched within the HTML of a creative, as these are fetched as part of the pre-caching process.

  • This will allow the bidder to find opportunities of potential efficiency improvements by finding areas of large drop offs between load and show. It will also be a critical piece to troubleshooting discrepancies.

4. Where should the bidder pass loadtrackers?

  • The loadtrackers array should be passed inside the bid extension object, in the same place as the imptrackers array: seatbid.bid.ext.loadtrackers

  • This field is optional, but if present, must be an object array of urls. We will invalidate any value that is not an array of strings, and they will be ignored as part of the bid response.

5. When will the loadtrackers fire?

  • Tracking URL’s submitted in this field will be fetched once an ad has been successfully loaded/pre-cached onto the device.

6. Which formats/sizes are supported?

  • SDK 4.19 - 5.3: HTML and MRAID for banners, MREC and fullsceen ads. VAST and Native are not supported.
  • SDK 5.4+: All sizes and formats.
  • Note: Partners wishing to only use this feature on fully supported versions and formats should look for the MoPub SDK version in the bidrequest.imp.displaymanagerver field of the bid request, and omit loadtrackers in their bid response if below 5.4.

7. How many loadtrackers can a bidder include in a bid response?

  • Bidders can submit one or more trackers.

Sample Response

  "bidid": "abc1234",
  "cur": "USD",
  "id": "1234567890",
  "seatbid": [
      "seat": "xyz12345",
      "bid": [
          "ext": {
            "imptrackers": [              "https://imptrackers1.com/mopub/win/${AUCTION_ID}/${AUCTION_BID_ID}/${AUCTION_IMP_ID}/${AUCTION_SEAT_ID}/${AUCTION_AD_ID}/${AUCTION_PRICE}/0.999",             "https://imptrackers2.com/mopub/win/${AUCTION_ID}/${AUCTION_BID_ID}/${AUCTION_IMP_ID}/${AUCTION_SEAT_ID}/${AUCTION_AD_ID}/${AUCTION_PRICE}/0.999"
            "loadtrackers": [             "https://loadtrackers1.com/${AUCTION_ID}/${AUCTION_BID_ID}/${AUCTION_IMP_ID}/${AUCTION_SEAT_ID}/${AUCTION_AD_ID}/${AUCTION_PRICE}/0.999"
            "nurls": [              "https://nurl1.com/mopub/win/${AUCTION_ID}/${AUCTION_BID_ID}/${AUCTION_IMP_ID}/${AUCTION_SEAT_ID}/${AUCTION_AD_ID}/${AUCTION_PRICE}/0.999",
          "id": "12345678",
          "adid": "314",
          "cat": [
          "adm": "",
          "adomain": [
          "bundle": "com.foo.mygame",
          "attr": [
          "cid": "campaign111",
          "crid": "101409",
          "h": 50,
          "w": 320,
          "impid": "1",
          "price": 0.999

Last updated August 28, 2021

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