HTML5 Banner Preview
MarketingDrop a banner ZIP or paste a tag, press Preview banner and watch it run — with what went wrong listed underneath.
Before a banner goes to an ad server, someone has to open it and watch it play — and double-clicking index.html in a ZIP is not the same as running it as an ad: relative paths break, scripts meant for a click tag misbehave, and nothing tells you what failed. Drop the ZIP (or an HTML file, or paste an iframe or script tag), press Preview banner, and it runs in a sandbox that cannot reach your cookies or this site, drawn at the size the creative says it is. Underneath: script errors, files that failed to load, what it printed to the console, the requests it made, and the size it actually drew. The same read checks the package against a publisher's rules — weight, file count, click tag, HTTPS — if you choose one. A ZIP is opened in your browser and never uploaded.
Need a different limit? HTML5 Ad Inspector takes any target, in KB or MB — whatever the form asks for.
Why do it here
100% private
Your creative files are processed locally and never uploaded.
Instant
No upload or download wait — it runs at the speed of your device.
Free to start
Use it free every day; go Pro for unlimited runs.
No install
Works in any modern browser. No sign-up to begin.
How it works
- 1Drop the banner
An HTML5 ZIP, an HTML file, or a pasted iframe or script tag.
- 2Press Preview banner
The preview starts at the creative's own size, in a sandbox. Replay it as often as you like.
- 3Read what happened
Errors, failed files, console output and requests are listed under the preview, with the publisher checks if you picked one.
Frequently asked questions
Is it safe to run a banner I did not make?
It runs in a sandboxed frame on an isolated origin: it cannot read cookies or storage, reach this page or navigate it. It can still make its own network requests — which is part of what the preview shows you.
Why does my banner work here but not on the ad server?
Ad servers add their own rules — a click tag variable, file limits, required HTTPS. Choose the publisher under Publishing on and the same package is checked against its published specification.
Can I preview a banner that is already live?
Paste its iframe or script tag. The tag is run as it would run on a page; the creative it loads comes from its own server, so what you see is what is live.
Is the ZIP uploaded?
No. The ZIP is opened in your browser and its files are fed to the sandbox from memory. A pasted tag loads from its own ad server, as it would on any page.