The custom weights feature in the ad manager lets you provide a weighted distribution for displaying creatives using the ad tag code.
How Custom Weights Work
The ad serving logic for the ad manager randomly selects a creative based on the weights, but does not strictly enforce the distribution. As a result, the served creatives may differ slightly from the provided weights.
For example, you can set up the distribution to favor two over the third if you have three creative files:
- Creative #1: 45%
- Creative #2: 45%
- Creative #3: 10%
With this setup, creatives #1 and #2 each receive about 45 impressions out of every 100, and creative #3 receives about 10 impressions.
You can think of this as each percent of creative weights being added to the list of the ad server for distribution. Creatives #1 and #2 would each be in the list 45 times, and #3 would be in list 10 times. When the ad server prepares the creative, it selects a random number between 1 and 100 that then corresponds to either creative #1, #2, or #3.
Here, creative #3 has a 10 in 100 chance of getting chosen. With a low volume of traffic, creative #3 could actually get chosen more frequently than 10%. But over time the randomness will be removed and the banner will be closer to 10 times out of 100.
If custom weights do not add up to 100%, then they are normalized to a total of 100%. Let’s say there were only 50 impressions, and the provided distribution is like this:
- Creative #1: 30%
- Creative #2: 19%
- Creative #3: 1%
In this case, the weights add up to 50% instead of 100%. TUNE scales these values up to what they would be with a total of 100%. So once normalized, creative #3 would appear approximately 2% of the time.
Because the distribution is normalized, these weights do not substitute for offer caps or limits. Caps must be set in the offer itself for an ad to be removed from the rotation.