Techniques for zero fixed placement (ZFP) ads are described. ZFP ads may be triggered independently of a fixed placement for the ad in a user interface. In an implementation, data describing a user interface includes a trigger associated with a ZFP ad. The ZFP ad may be configured to set various modifiable attributes of the user interface. Setting the modifiable attributes of the page enables a ZFP to modify both the appearance and layout of elements and modules included in the user interface. A client may load the data having the trigger and render the user interface without presenting the associated ZFP ad or including a placeholder for the ZFP ad. When the trigger is detected, the client executes the associated ZFP ad, modifies attributes of the user interface in accordance with the ZFP ad, and outputs the modified user interface to present the ZFP ad.