Crypto banner ads: sizes, formats and what gets rejected

Six image sizes are accepted on PraxAds: four standard IAB display sizes and two native sizes. That's the complete creative surface area for crypto banner and native ads on our network, and it's smaller than you'd get elsewhere on purpose. We take images in PNG, JPG, GIF or WebP. A native ad adds a headline, your brand name and an optional line, all as plain text. We don't accept HTML or JavaScript creatives at all. A banner that can't execute code can't fingerprint devices, redirect users, or carry a payload, and in crypto advertising that class of abuse is exactly what publishers and readers have learned to expect.

Here's what to build, at what size, and what will get a creative sent back.

The sizes and where they run

The campaign form lists the accepted dimensions when you upload. The four display sizes map directly to the fixed-size units in the IAB Standard Ad Unit Portfolio (July 2017, version 1.1):

• 300x250, medium rectangle, in-content and sidebar slots and mobile
• 728x90, leaderboard, top of page on desktop
• 300x600, half page, desktop sidebar
• 320x50, smartphone banner, anchored to the bottom of a mobile screen

The other two accepted sizes, 1200x630 wide and 1200x1200 square, sit outside the IAB fixed-size set and serve native placements. A native ad is one of those images plus plain text: a headline of up to 60 characters, your brand name of up to 25, and an optional line of up to 90. The ad server adds a Sponsored label next to your brand name. It writes that word itself, and you can't reword or remove it.

If you make only two, make the 300x250 and the 320x50. The medium rectangle runs in the widest range of contexts, and the smartphone banner covers mobile, where a large share of crypto traffic lives. If you make four, add the 728x90 and the 300x600.

File weight, resolution, and the mobile reality

The IAB portfolio publishes file weight guidance per unit, and it's worth respecting even where a network doesn't hard-enforce it: 150 kB initial load for a 300x250 or a 728x90, 200 kB for a 300x600, and just 50 kB for a 320x50. A heavy banner loads late, and a banner that loads after the reader scrolls past the slot is an impression you paid for and nobody saw.

Export at exactly the accepted pixel size, then compress. The upload reads the file's real dimensions and refuses any other size. WebP typically lands well under the weight guidance. Test the result at actual size on a phone, since a 320x50 viewed on a designer's monitor at 400 percent zoom tells you nothing about legibility in the wild.

Design-wise, the constraints of a small static image are your friend. One line of text a reader can process in under a second, one visual element, one button-shaped call to action, your name or logo. If the value proposition needs a paragraph, the paragraph belongs on the landing page.

Why no advertiser code is a feature

HTML5 creatives can animate, expand, and adapt. They can also spawn pop-ups, chain redirects, mine data, and deliver malware, and rich media has been a recurring vehicle for all of these across the ad industry. We removed the category of risk instead of trying to police it. Static and simple animated images can't execute anything. Neither can the plain text on a native ad, which the ad server writes as text, not markup.

For you as an advertiser, the practical consequences are mostly positive. Production is cheaper and faster. Files are reviewable at a glance, which keeps our moderation inside our published 24-hour window. And publishers accept the placements more readily, because nothing in the creative can damage their page or their readers.

Animated GIFs are allowed within the format list. Keep loops short and avoid strobing effects, and remember the file weight guidance applies with more force to animation than to stills.

What gets crypto banner ads rejected

Every creative on PraxAds is reviewed by a person before it serves, and every rejection comes back with a written reason. These are the reasons we write most.

• Guaranteed or implied guaranteed returns, "100x", "risk-free", fixed profit percentages
• Fake interface elements, counterfeit system dialogs, imitation play buttons, or fake close buttons designed to harvest misclicks
• Mismatch between the creative's claim and the landing page it links to
• Impersonation of exchanges, wallets, tokens, or public figures
• Unreadable text, stretched or blurry images, or missing advertiser identity

Two patterns are worth spelling out. The mismatch rule means we review the banner and the destination together, so a compliant image linked to a page promising guaranteed yield fails as a unit. And the fake-UI rule exists because tricked clicks poison everyone: the reader who got deceived, the publisher whose page did the deceiving, and you, since a click obtained by trickery converts at approximately zero and you paid for it.

A rejection isn't a ban. Fix the stated issue, resubmit, and your prepaid balance is untouched throughout, since campaigns only draw down when impressions actually serve.

Build for the click after the click

You can check whether your banners work because every placement carries UTM tags that land in your own GA4. That changes how you should design. A curiosity-gap banner ("You won't believe this chart") can win clicks and still lose money, because the sessions it produces bounce immediately. A plain banner that states the product filters out everyone who was never going to convert, before you pay for the click on a CPC campaign or burn the impression's attention on a CPM one.

Our auction sharpens this further. Allocation weights each bid by smoothed click-through rate, so a creative that earns clicks honestly wins more of the available impressions at the same bid price. The system pays you in delivery for making banners people genuinely want to click.

If your banner needs trickery to get clicked, the problem is the offer, and no file format will fix it.

Run two creatives per size from day one, let the click-through data pick the winner, and retire the loser without sentiment. The IAB's guidance puts a 320x50 smartphone banner at 50 kB on initial load, a third of what a 300x250 is allowed.