Ad Slot Sizes
Understand ad dimensions and choose the right sizes for your slots.
Size basics
Ad sizes are defined as width × height in pixels: 300x250 = 300 pixels wide, 250 pixels tall.
Common sizes
Desktop
| Size | Name | Best for | Demand |
|---|---|---|---|
| 728x90 | Leaderboard | Headers | High |
| 970x90 | Large leaderboard | Wide headers | Medium |
| 970x250 | Billboard | High-impact headers | High |
| 300x250 | Medium rectangle | Sidebar, in-content | Highest |
| 336x280 | Large rectangle | In-content | High |
| 300x600 | Half page | Sidebar | High |
| 160x600 | Wide skyscraper | Sidebar | Medium |
| 120x600 | Skyscraper | Narrow sidebar | Low |
Mobile
| Size | Name | Best for | Demand |
|---|---|---|---|
| 320x50 | Mobile leaderboard | Header, sticky footer | High |
| 320x100 | Large mobile banner | In-content | High |
| 300x250 | Medium rectangle | In-content | Highest |
| 320x480 | Mobile interstitial | Full-screen | Medium |
Special formats
| Size | Name | Description |
|---|---|---|
| Fluid | Responsive | Adjusts to container |
| Native | Content-matched | Blends with page design |
Choosing sizes
By position
| Position | Recommended | Why |
|---|---|---|
| Header | 728x90, 970x250 | Standard top placements |
| Sidebar top | 300x250, 300x600 | High viewability |
| Sidebar bottom | 300x250, 160x600 | Fallback options |
| In-content | 300x250, 336x280 | Fits text flow |
| Sticky footer | 728x90 (desktop), 320x50 (mobile) | Persistent visibility |
By goal
| Goal | Strategy |
|---|---|
| Maximize CPM | Use 970x250, 300x600 — larger formats command premiums |
| Maximize fill | Use 300x250, 728x90 — highest demand |
| Balance both | Multi-size slots: 300x250 + 300x600 |
Multi-size slots
You can assign multiple sizes to one slot. Ads compete across sizes.
Pros
- More advertiser competition
- Better fill rates
- Potentially higher CPMs
Cons
- Less predictable layout
- May cause layout shift (CLS)
- Harder to design around
Recommended combinations
| Slot type | Size combination |
|---|---|
| Leaderboard | 728x90 + 970x90 + 970x250 |
| Sidebar | 300x250 + 300x600 |
| In-content | 300x250 + 336x280 |
| Mobile header | 320x50 + 320x100 |
More sizes means more variability. Keep it manageable.
Size performance
Different sizes have different characteristics:
| Metric | Larger sizes | Smaller sizes |
|---|---|---|
| CPM | Generally higher | Generally lower |
| Fill rate | Lower (less demand) | Higher (more demand) |
| Viewability | Depends on placement | Depends on placement |
Viewing size performance
- Go to Dashboard → Monetization
- Add Size as a dimension
- View CPM, fill rate, revenue by size
Use this data to optimize your size selections.
Size and layout shift
Multi-size slots can cause Cumulative Layout Shift (CLS) — content jumping as ads load.
Prevention strategies
Reserve maximum space:
.ad-container {
min-height: 250px; /* Height of largest size */
min-width: 300px;
}
Use aspect ratio:
.ad-container {
aspect-ratio: 300 / 250;
max-width: 300px;
}
Prefer single sizes for sensitive positions:
- Above-the-fold headers
- Adjacent to main content
IAB standards
These sizes follow IAB (Interactive Advertising Bureau) standards, ensuring compatibility across ad networks.
| Category | Sizes |
|---|---|
| IAB Rising Stars | 970x250, 970x90, 300x600 |
| Universal Ad Package | 728x90, 300x250, 160x600, 180x150 |
| Mobile | 320x50, 320x480, 300x250 |
Common questions
Which size has the best CPM?
Generally, larger sizes (970x250, 300x600) have higher CPMs because they're more impactful.
However, 300x250 often generates the most total revenue due to high fill rates and demand.
Should I use non-standard sizes?
Generally no. Non-standard sizes have:
- Less advertiser demand
- Lower fill rates
- Potential compatibility issues
Stick to IAB standard sizes unless you have a specific reason.
How do I handle responsive design?
Options:
- Use fluid/native sizes — Adapt to container
- Device-specific layouts — Different layouts for mobile/desktop
- CSS media queries — Show/hide slots by screen size