## [What is Cost ID?](what-is-cost-id)

__Cost ID__ is a unique ad spend engagement identifier value between 12 and 256 characters in length. Adjust uses the `cost_id` parameter to match the received ad spend data with a click or impression.  

Here are some points to consider when using `cost_id` with the Partner ad spend push API:

*   To avoid matching a value from one of our other network partners, the `cost_id` value must be *unique*. We recommend using a __Universally Unique Identifier (UUID)__ or prefixing your ID with your company’s name. For example: `network_name_848dsf4939fgwjn028erg4`.

*   You can use your pre-existing `click_id` or `impression_id`. If you do not generate your own click or impression IDs, then you can combine two or more placeholders to form it. For example for CPI, you could combine the user’s IDFA and the app ID.

## [Measuring CPM with Adjust](measuring-cpm-with-adjust)

To send CPM data to Adjust, send `cost_id` through the impression URL and refer to it in the partner ad spend push API call. Ensure that you send the CPM with each impression.


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