Waterfall Latency

MoPub has powerful tools to help you manage the waterfall for your ad inventory. Each item in your waterfall is a call to an ad source. If no ad is returned by the ad source, the next item in your waterfall is chosen. For each ad source, MoPub has to make a call to retrieve ads, either internally or to a partner, which takes time and affects the interval between the moment when the ad request is initiated and the moment when the ad response is returned. This interval is called latency.

Latency Example 1

Read this article to learn the causes of waterfall latency and how to minimize it. As a rule of thumb, a high number of ad sources in your waterfall causes higher latency.

Latency by Ad Source Type

Ad sources fall in to four types. Each type of ad source impacts ad serving latency differently:

  • Direct Serve ads: These are ads that you, as the publisher, sell directly to yourself as the advertiser, in the Orders tab in the MoPub UI. They are served from MoPub’s ad serving infrastructure, which has a latency of up to 100 ms per qualifying line item. A qualifying line item is a line item targeted to the ad request.

  • MoPub Marketplace: The MoPub Marketplace lets MoPub fill your ad impressions by reaching out to demand-side platform partners (“DSPs”), and asking them in real time to bid on your impressions. The DSPs have a maximum timeout period of 200 ms to respond to the bid request, and there can be up to 100 ms in additional processing time, resulting in a total maximum of 300 ms per MoPub Marketplace request.

  • MoPub ad network SDK mediation: For our supported mediation partners, such as AdMob and Facebook, MoPub lets publishers to drop in that ad network’s SDK. MoPub can then direct ad requests to that SDK via mediation. In the case of SDK mediation, the ad network’s SDK controls the timeout, and thus the maximum latency. To prevent extreme delays, MoPub limits these SDKs to a maximum timeout of 10 seconds for banners and native ads, and 30 seconds for interstitials.

  • Custom JavaScript networks: While JavaScript tags from custom networks are supported through the MoPub UI, we discourage the use of this functionality, and do not provide technical support for issues arising from networks’ tags. We recommend using no more than two tags, because there are adverse downstream effects of using this method.

In addition to the ad serving latency discussed above, our the end-to-end calculation must also account for latency in the internet. MoPub’s ad serving infrastructure is located in the continental United States.

This table summarizes the 5 different types of latency sources:

Type Timeout / Maximum Latency Who sets the timeout?
Direct Serve ads via MoPub 100 ms MoPub
MoPub Marketplace 200 ms MoPub
MoPub SDK mediation Ad network’s SDK controls timeout.

In addition, MoPub SDK times out after:
- 10 seconds for banners, native
- 30 seconds for interstitials, rewarded videos
Supported mediation partner
Custom Javascript network Custom JavaScript network controls timeout. Custom Javascript network
Internet latency Up to several seconds Internet provider, geographical distance to MoPub data center

Best Practices

We recommend the following best practices to minimize your waterfall latency:

  • Minimize number of waterfall items: More waterfall items result in higher average and maximum latencies. If you have a very complex waterfall, consider removing low-CPM and low-fill network partners, especially for SDK-integrated networks.

  • Keep items at the same priority: If you set up your waterfall items at the same priority, then MoPub Marketplace, SDK networks, and Direct Serve ads can compete with each other for the maximum CPM. We are obligated to show a network’s creative anytime we reach out to a network and it successfully returns a creative, so we must wait until both Marketplace and your network partner have returned a result. Setting the items at the same priority enables us to send concurrent requests and improves both your latency and CPMs.

  • Manage banners and native ad unit waterfalls more aggressively than interstitials. Banners and native ad units appear on the screen shortly after setting up the view, while interstitials are often pre-loaded in the background, and shown at a later state. Thus, interstitials waterfalls can be more complex than the ones for banners without compromising the user experience.

Last updated August 24, 2020

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