HTML5 banner ad specs by platform

File size caps, clickTag conventions, animation limits and external-asset rules for 10 ad platforms — each figure paraphrased from the platform's own documentation and dated. 4 of 10 records have had every constraint sourced from a primary document; the rest show only what we can cite and stay silent on the rest.

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Fully sourced records only

HTML5 banner requirements by ad platform. An em dash means the platform has not published that figure, or we have not yet sourced it.
		Files	Click	Element links	Animation	External assets
AdformAd server	300 KB unzipped	—	clickTag variable`clickTAG`	Supported	30s	External assets allowed	20 September 2026
AdRollNetwork	150 KB zipped	—	clickTag variable`clickTag`	One per banner	30s	Everything must be in the ZIP	20 September 2026
Campaign Manager 360Ad server	10 MB zipped	100	clickTag variable`clickTag`	One per banner	—	—	limits unverified
Display & Video 360DSP	No stated cap	100	clickTag variable`clickTag`	One per banner	30s	—	limits unverified
General usageStandards body	—	—	—	Supported	—	—	limits unverified
Google Ad ManagerSSP	1 MB zipped or unzipped	—	clickTag variable`clickTag`	One per banner	—	External assets discouraged	20 September 2026
Google Ads (Display)Network	600 KB zipped	40	—	One per banner	—	Approved hosts only	limits unverified
Sizmek (Amazon Ad Server)Ad serversunsetting	—	—	—	One per banner	—	—	limits unverified
Xandr (Microsoft Advertising)DSP	—	—	clickTag on the ad URL`clickTag`	One per banner	—	—	limits unverified
Yahoo DSPDSP	1 MB zipped	—	clickTag variable`clickTag`	One per banner	15s	External assets discouraged	20 September 2026

How to read this table

An em dash is not a zero. It means the platform publishes no figure for that constraint, or that we have not yet sourced one. We would rather print nothing than a number that gets your campaign rejected, so a cell is filled only when we can quote the document it came from.

Max ZIP size says what it measures. A cap on its own is ambiguous — 1 MB zipped and 1 MB unzipped are different numbers for the same bundle, and Google Ad Manager caps whichever of the two is larger. A creative that zips under the cap and expands past it is the most common way a package passes a naive checker and is still refused on upload.

Verified means sourced, not blessed. A dated row had every constraint read off the platform's own documentation on that date. An unverified row is not a guess — it shows only the fields we can cite and leaves the rest blank.

Common questions

What is the maximum file size for an HTML5 banner?

There is no single answer — it is set by the platform, not by the format. Among the platforms above the published caps run from 150 KB to 10 MB, and one states no cap at all. Check the row for the platform you are delivering to, and note whether the cap is measured zipped or unzipped.

Do I have to set the clickTag value before I export?

It depends on the platform. Most ad servers rewrite the clickTag at trafficking time, so an empty value in the file is correct and expected. Others never rewrite it, and an empty value ships a banner whose click area goes nowhere. Each platform page says which behaviour applies.

Can an HTML5 banner load fonts or libraries from a CDN?

On some platforms yes, on some only from an approved list of hosts, and on some not at all — everything must be inside the ZIP. It is one of the most common reasons an otherwise valid package is refused on upload, so it has its own column above.

How current is this data?

Each platform page carries the date its requirements were last read from the source, and every figure links to the document it came from. Records are re-verified on a six-month cycle. This is an unofficial reference — confirm anything critical with your platform before delivery.

Every platform

Foldwrap exports native HTML5 to these platforms from one editable creative, and checks every package against the rules above before it is delivered. See how HTML5 export works.