What is the 300×50 Mobile Banner?
The 300 x 50 Mobile Banner is one of the original standard ad units for smartphones. Often called the “Mobile Leaderboard” (though slightly smaller than the 320×50), it serves as a critical fallback size for smaller devices and tight layout spaces where larger banners won’t fit.
While larger sizes like the 320×100 are becoming more popular, the 300×50 remains essential for maximizing fill rates across diverse mobile inventory, especially on older devices or compact app interfaces.
Why Use the 300×50 Size?
- Universal Compatibility: Fits almost every smartphone screen in existence.
- Non-Intrusive: Sits quietly at the top or bottom of the screen without blocking content.
- High Fill Rate: Because it is a legacy standard, there is massive demand from ad networks to fill this slot.
Technical Specifications
- Dimensions: 300 pixels wide by 50 pixels tall.
- File Weight: 150KB (Max).
- File Formats: JPG, PNG, GIF, HTML5.
Best Practices for Design
With only 50 pixels of height, you have very little vertical space. Keep your design simple: use a clear, bold headline and a high-contrast “Call to Action” button. Avoid complex imagery or small text that will be unreadable on a phone screen.