What Are Ad Slots?
An ad slot represents a single ad placement on your website — the exact location where an ad will appear.
Understanding ad slots
Think of an ad slot as a reserved space on your page. When a user visits your site, this space fills with an advertisement selected through the header bidding process.
Ad slot components
Each ad slot has several key properties:
| Property | Description |
|---|---|
| Name | A unique identifier you create |
| ID | System-generated unique identifier |
| Sizes | Allowed ad dimensions (e.g., 300x250, 728x90) |
| Demand wiring | A partner bids on a slot when you map its tag ID to the slot (on the demand seat's Tag IDs tab) — it isn't a field on the slot itself |
Common ad slot positions
| Position | Typical sizes | Description |
|---|---|---|
| Leaderboard | 728x90, 970x90 | Top of page, below header |
| Sidebar | 300x250, 300x600 | Right or left column |
| In-content | 300x250, 336x280 | Within article body |
| Sticky footer | 728x90, 320x50 | Fixed at bottom of viewport |
| Interstitial | Various | Full-screen overlay |
Ad slots vs. ad units
Ad slots are your internal organization of placements. Ad units are what Google Ad Manager uses. When you connect GAM, you can link your ad slots to GAM ad units.
How ad slots work
Page loads → Ad slot found → Header bidding runs → Winning ad displays
- Your page loads with the wrapper tag
- The wrapper identifies ad slots on the page
- Demand partners bid on available slots
- The highest bidder's ad displays