The Google Ads API lets you retrieve bid simulation data, which can help you
estimate how changes to bids, targets, or budgets might impact your
performance for key metrics like cost, clicks, impressions, and conversions.

## Use case

Suppose you have an ad that's been running for a few weeks, and it is 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 impressions 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? How do you 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 impressions, 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, targets, and
budgets for the future.

## API capabilities compared to the Google Ads UI

The API provides access to simulation data through the following resources:

- **Campaigns ([`campaign_simulation`](https://developers.google.com/google-ads/api/fields/v26/campaign_simulation)):** Simulates the impact of budget changes, CPC bid changes, Target CPA or Target ROAS target changes, and Target Impression Share changes.
- **Ad groups ([`ad_group_simulation`](https://developers.google.com/google-ads/api/fields/v26/ad_group_simulation)):** Simulates the impact of changing ad group-level CPC or CPV bids, or Target CPA or Target ROAS targets.
- **Ad group criteria
  ([`ad_group_criterion_simulation`](https://developers.google.com/google-ads/api/fields/v26/ad_group_criterion_simulation)):** Estimates the effects of keyword or listing group CPC bid changes and Hotel listing group percent CPC bid changes.
- **Bidding strategies
  ([`bidding_strategy_simulation`](https://developers.google.com/google-ads/api/fields/v26/bidding_strategy_simulation)):** Assesses outcomes for portfolio Target CPA or Target ROAS bidding strategy changes.

This functionality is similar to the bid simulator features available for these
entities within the Google Ads UI. However, the API's focus is on providing the
raw simulation data. It may not encompass all the specialized simulation
visualizations, tools, or simulation types present in the Google Ads UI.

## How to use API bid simulations

To programmatically retrieve and use bid simulation data, query the simulation
resources in the API. These resources provide point estimates for different bid,
target, or budget values.

Before querying bid simulations, review the [Prerequisites](https://developers.google.com/google-ads/api/docs/bid-simulations/prerequisites) for
account and traffic requirements and supported channel types. For a
comprehensive list of available simulation resources, fields, and code examples,
see [Retrieve bid simulations](https://developers.google.com/google-ads/api/docs/bid-simulations/retrieve-bid-simulations).

> [!NOTE]
> **Note:** When you read the [Google Ads Help Center article about bid
> simulators](https://support.google.com/google-ads/answer/2470105), be aware that the article describes the full range of features available in the Google Ads UI. This API guide focuses specifically on the data and capabilities accessible programmatically with the Google Ads API.