What are creative specifications for ads?
What creative specifications cover, why they matter for readers and delivery, and how to publish them.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readCreative specifications (ad specs) are the technical rules an ad must follow to run on a publisher’s site: sizes, file types, file weight, animation, sound and tracking.
What specs cover
| Spec | Example |
|---|---|
| Sizes | 300×250, 980×240, 320×320 |
| File types | HTML5, JPG, PNG, MP4 |
| File weight | A maximum initial load per ad |
| Animation and sound | Length limits, sound off by default |
| Tracking | Allowed third-party tags |
Why they matter
Fast pages
Heavy ads slow the site for everyone.
Smooth delivery
Fewer rejected creatives and delays.
Reader trust
No intrusive or broken ads.
16 pages for publishers, with a checklist for data, programmatic and direct sales.
Publish them clearly
Put specs and deadlines in your media kit and on your website, so agencies can build the right ads the first time.
More ad sales with data at Stampen Media, using Samhub.
Frequently asked questions
Each publisher, often based on IAB guidelines.
It is usually rejected or sent back for changes.
Most publishers ask for a few working days before start.
Programmatic ads follow the same sizes, checked by the SSP or ad server.
Related terms
The ad sizes every buyer and ad server supports.
Ads with video, animation or interaction.
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