Ad Banner Placeholder Sizes (IAB Standard)

Ad Banner Placeholder Sizes

The Interactive Advertising Bureau (IAB) defines standard ad unit sizes used across the web advertising ecosystem. When designing websites that include ad placements, you need placeholder images that match these exact dimensions to ensure your layout accommodates ads correctly.

IAB Standard Ad Sizes

Ad Unit	Dimensions	Common Name
Medium Rectangle	300×250	The most popular ad size
Leaderboard	728×90	Top-of-page banner
Wide Skyscraper	160×600	Sidebar vertical
Mobile Banner	320×50	Mobile header/footer
Large Rectangle	336×280	Enhanced medium rectangle
Half Page	300×600	High-impact sidebar
Billboard	970×250	Premium top banner
Mobile Interstitial	320×480	Full-screen mobile
Large Leaderboard	970×90	Wide top banner

Generating Ad Placeholders

1. Enter the exact width and height for your target ad unit
2. Set a distinctive background color (e.g., a light gray or brand accent) so the ad area is visually clear in your layout
3. Add text like "AD 300×250" to label the placeholder
4. Download and insert into your development layout

Why Accurate Ad Placeholders Matter

Using correctly sized ad placeholders during development prevents common issues:

• Layout shifts — Content jumping when real ads load (hurts Core Web Vitals CLS score)
• Overflow bugs — Ads breaking out of their containers because the container was sized for the wrong dimensions
• Responsive issues — Ad containers not scaling properly between breakpoints
• Stakeholder confusion — Designers and clients cannot evaluate page balance without seeing the space ads will occupy