Banner Ad

Banner Ad is the rectangular display ad you see in the header, sidebar, or between content blocks of a website. The original web ad format, dating back to 1994, and still the bedrock of programmatic display advertising despite being declared dead approximately every two years since 2007.

Standard sizes that actually get used

The IAB (Interactive Advertising Bureau) maintains a long list. Five do most of the work:

728×90 leaderboard - top of desktop pages, classic header slot.

300×250 medium rectangle - the highest-CTR unit, sits inside content. The workhorse of AdSense and most ad network inventory.

300×600 half-page - sidebar real estate, premium pricing because it dominates the visual.

320×50 mobile leaderboard - the standard mobile sticky.

970×250 billboard - high-end takeover slot, used for big brand campaigns.

Outside these, you’re either custom-building or buying inventory nobody actually wants.

Why CTRs are so bad and why it doesn’t always matter

Average display CTR sits around 0.05-0.1%. That’s one click per thousand impressions on a good day. Compared to paid search (3-5%) or email (2-3%), banner ads look broken.

They’re not - they’re playing a different game. Banner ads work on the awareness/recall layer, not direct response. The brand impression registers even when nobody clicks. Studies on view-through conversion (people who saw an ad, didn’t click, then converted later via search or direct) consistently show banner ads lifting demand even when click data shows nothing.

That said, most small-budget direct-response campaigns shouldn’t be running banner ads. Spend on search and social where intent is hotter.

The two things that decide whether your banner ad works

Targeting beats creative. A boring ad served to the right person beats a clever ad served to the wrong one. Most banner-ad disappointment is targeting failure dressed up as creative failure.

Frequency capping. Show the same person your ad three times and they might notice. Show them thirty times and they actively dislike your brand. Set a frequency cap of 3-5 per week per user as a default and only raise it for genuine campaign reasons.

An example of when it actually pays

A B2B SaaS targeting marketing operations managers ran a six-week banner campaign on three industry publications they identified as where their buyers actually read. CPM $14, total spend $18k, total impressions 1.3M, clicks roughly 900 (0.07% CTR - exactly average for display).

Direct conversions from clicks: 4 trial signups. On its own, atrocious ROI.

But branded search volume from companies in their target list lifted 23% over the campaign window. Total trial signups from those companies (across all attribution paths) lifted 60%. The banner ad wasn’t generating clicks - it was warming up an audience that converted somewhere else. The $18k spend produced ~30 attributable trial signups when measured at the audience level, not the click level.

Related terms

• Display Ads - the broader format category banner ads are the originating shape of
• Ad Network - the distribution layer that places banner ads at scale
• AdSense - the publisher-side product that monetises most banner inventory
• Impression - the unit banner-ad campaigns are usually priced and judged on
• Cost Per Impression (CPM) - the standard pricing model for banner ad placement