Preflight your HTML5 banner
Check a banner against an ad network's real requirements — size, animation duration, dimensions, required tags, click integration, and forbidden external sources — before you upload it.
Provide the banner
ZIP, a single HTML file, or pasted code.
Choose ad network
We pre-select it from the banner when we can — limits and rules load automatically.
Awaiting input
Pick a network and add a banner to see the report.
Use Banner Check with your AI tools
Install the validate-banner skill & CLI, or explore the ChatGPT MCP preview. Your files are processed locally in both.
Catch banner rejections before the ad server does
Ad networks bounce HTML5 creatives for small, avoidable reasons — an oversized ZIP, a timeline that never stops, a missing or malformed clickTag, dimensions that don't match the declared ad.size, or an external font URL that a strict DSP like Amazon forbids. Banner Check runs every one of those checks right in your browser, so you catch problems in seconds instead of waiting on a rejection. Nothing is uploaded — your files never leave your machine.
It's built by Viewst, an AI ad-production platform that exports network-ready HTML5 banners at scale, and the ruleset mirrors Viewst's live ad-network export pipeline.
A dedicated validator for every ad network
Each network has its own page with that network's exact size limit, click integration, animation policy, required vendor scripts and external-URL policy. Open one to validate against a single network or to read its full requirements: