Standard banner ad sizes that actually perform

Most teams either build too few sizes and miss inventory, or build too many and never maintain them. The fix is to cover the standard set from one dynamic master, then let performance decide where budget flows.

Which banner sizes carry the inventory?

Four units hold most of the available display inventory: 300×250, 728×90, 160×600 and 336×280. The table below is the set we build by default. The ones marked with a star are the high-inventory four.

What are the Google Ads file rules?

This is where good creative dies on upload. A Google Ads HTML5 ad is a ZIP of up to 600 KBwith no more than 40 files; a static image ad is capped at 150 KB. Animation has to stop within 30 seconds. Note the common myth: the old 150 KB figure is the image-ad limit, not the HTML5 limit. Many exchanges still apply a stricter initial-load cap, so keep libraries out and assets compressed.

How much does the size choice matter for clicks?

Less than the creative inside the frame. Cold display click-through sits around 0.05%–0.1% and retargeting near 0.7% regardless of size. Larger formats such as 300×600 and 336×280 tend to be more viewable, which helps, but a sharp message in a 300×250 beats a dull one in a billboard. We cover this trade-off in display creative & DCO.

Responsive or fixed display ads?

Responsive display ads let Google assemble the unit from a few headlines, images and a logo, then stretch it to fit almost any placement. They are a sensible baseline for reach and the fastest way to cover odd slot sizes. The trade-off is control: you do not decide the exact layout, animation or how the message reads at each size. Fixed HTML5 units give that control back, which is why brands that care about how a banner looks and converts run them on their priority placements.

In practice we run both. Responsive ads mop up long-tail inventory, while a fixed HTML5 set built across the 300×250, 728×90, 160×600 and 336×280 workhorses carries the placements that actually drive conversions. That mix keeps reach high without surrendering the creative quality that moves view-through and cost per acquisition.

Do not forget mobile

A large share of display impressions are served on phones, so mobile units are not optional. The 320×50 mobile leaderboard is the standard anchor banner; 320×100 (the large mobile banner) doubles the height and earns noticeably more attention for brand messages. The same 600 KB and 30-second animation limits apply, but mobile punishes weight harder: heavy banners load late, miss the viewability window, and waste the impression. Keep mobile units especially lean and make sure tap targets are large enough to avoid accidental clicks, which exchanges treat as invalid traffic.

A pre-launch checklist for every banner

Before a single unit goes live, we run each one through the same short list. It is unglamorous and it is what keeps creative from dying on upload or under-performing in the wild.

• File weight under the 600 KB HTML5 budget (and under any tighter exchange initial-load cap), with assets compressed.
• A static backup image supplied for every size, so placements that reject HTML5 still show a banner.
• A correctly wired clickTag, so clicks track and the exit URL can change without a rebuild.
• No external network calls or auto-play audio, which exchanges and Google Ads reject.
• Animation that stops within 30 seconds and reads clearly in its first two seconds, before anyone scrolls past.
• Legibility checked at 100% and on high-density screens, with brand-safe contrast on every size.

Build once, ship every size

The practical answer is a dynamic HTML5 master: one design that outputs all the sizes above and updates from a live feed. It removes the hand-resizing that makes static banner sets so slow, and it is exactly how we lifted a travel brand's retargeting click-through in our creative case study. When you are ready to act on it, the free audit is the place to start.