300x250 — Medium Rectangle

Actual size

Rendered at true pixel dimensions. On a narrow screen it scales down to fit.

Where it runs

In-article or sidebar, usually within the first screen of content. The one size that works essentially everywhere.

Why it is used

The most widely traded display size in the world, and the one to include if you only produce one creative. Its dominance is self-reinforcing: because every publisher supports it, every advertiser makes it, so it carries the deepest demand and the highest fill of any unit. It also survives the transition to mobile better than any other desktop size, since 300 pixels fits comfortably inside a 320-pixel-wide phone viewport.

What to watch for

Its ubiquity means the most competition, so it is rarely the cheapest inventory. And because it appears both in-article and in sidebars, viewability varies enormously by placement — the same size can measure 70% viewable in one position and 30% in another on the same site.

Related sizes

• 336x280Large Rectangle
• 300x600Half Page
• 728x90Leaderboard