# Substitution Macros

### Click tracking

Click tracking is supported using a macro. The macro can be used only for banners. The macro should not be used for video, audio, and native ads due to the specific of their protocols.

The macro can be anything.

SSP is strictly required to always redirect to the passed URL exactly, without applying any of its own algorithms to the redirection.

SSP should replace the macro with a non-URL-encoded URL, for example, `https://ssp_domain/click?dst=`, where the `dst` parameter should accept the URL for redirection. The redirection URL may be URL-encoded or not. Discussed individually with each SSP.

For example, the bid response markup:

`<a href="${CLICK_URL}http%3A%2F%2Fexample.com%2F"></a>`

after replacing the macro:

`<a href="https://ssp_domain/click?dst=http%3A%2F%2Fexample.com%2F"></a>`&#x20;

### Supported auction macros

| Name                         | Description                                             |
| ---------------------------- | ------------------------------------------------------- |
| **${AUCTION\_PRICE}**        | Clearing (billable) CPM price.                          |
| **${AUCTION\_BID\_ID}**      | ID of the bid; from `BidResponse.bidid` attribute.      |
| **${AUCTION\_IMP\_ID}**      | ID of the impression just won; from `imp.id` attribute. |
| **${AUCTION\_LOSS}**         | Loss reason code.                                       |
| **${AUCTION\_MIN\_TO\_WIN}** | The minimum bid to win of the auction in CPM.           |
