Bid simulations allow you to estimate performance for your ad groups, criteria, and campaigns under different bidding scenarios. You can use this information to adjust and optimize your bidding strategy.
The bid simulations of Google Ads API predict how changing your bid in various ways impacts cost, impressions, and clicks. This is analogous to bid simulators in the Google Ads UI and is based on historical data. For forward-looking predictions you can refer to the similar concept of keyword planning.
Use case
Imagine you have an ad that's been running for a few weeks, that's costing a lot more than you expected or wanted to spend.
You want to test what might happen if you lower your bids a little. How many fewer views and clicks would your ad get? How much less would it cost? Conversely, what if your ad isn't getting the number of impressions and clicks you expect, and you want to know where you should set your bids to fix that problem?
Bid simulations help you research these scenarios. When you fetch a bid simulation, it shows projected views, clicks, and cost during the time period your ad was showing.
With bid simulations you can examine performance statistics for the past week at the current level of bidding, alongside simulated performance over the same time period using different bid amounts.
By analyzing how your ads might have performed differently in the past, you can make more informed decisions about how to adjust your bids and campaign-level bid modifiers for the future.