Terms

Last updated 23 August 2026.

These terms govern vastlint.org, the hosted tester, inspector, and validator, the IAB Tech Lab VAST Tester fork we host, related APIs, and the CLI when you send a sample. Using those tools means you accept these terms. If you do not accept them, do not paste, fetch, or contribute a tag. Privacy describes what we keep. These terms describe what you allow us to do with it.

Submitting a tag

If you paste XML, drop a file, fetch a URL, share a tag, or pass --contribute-sample, you are submitting that tag. You represent that you have the right to submit it, that you are authorized to let us handle it as described here, and that doing so will not violate any contract, insertion order, privacy law, or third-party right. Do not submit a live production tag unless you accept that we may treat it as a development sample.

License

You grant the operator of vastlint.org a worldwide, royalty-free, irrevocable, non-exclusive license to copy, store, parse, transform, retain, and use submitted tags and any URLs, wrappers, media, tracking, verification, or other resources they contain, for operating the tools and for developing, testing, and improving validation rules and related products. That includes asking our systems or a human maintainer to:

• fetch wrapper chains and other hops
• request MediaFile, Mezzanine, and similar creative URLs
• request Impression, Error, Tracking, ClickTracking, clickthrough, verification, and other beacon or pixel URLs (those requests can fire vendor beacons)
• replay, redact, cluster, or derive fixtures and rules from the XML

We do not sell tags. We do not publish submitted XML as a public gallery. We may keep a sample after you opt out in the browser; opt-out stops new sends from that browser, it does not recall tags already stored.

Beacons and live URLs

VAST documents are live instructions. Fetching or probing a submitted tag can cause third-party servers to record impressions, errors, clicks, or other events, and can consume media bandwidth. You authorize that. You will not claim that we stole the tag, hijacked the campaign, generated invalid traffic, or owe make-goods, ad spend, fill, or similar damages because we stored the tag or requested URLs in it for development. If you need a tag that must never be requested, do not put it here. Use placeholders or a dedicated QA endpoint.

No warranty

The site and tools are provided as is, for QA and engineering. We do not warrant that validation is complete, that a green result will pass any exchange, or that probing a tag is safe for production. Use at your own risk.

Limit of liability

To the maximum extent permitted by law, the operator of vastlint.org is not liable for lost profits, ad spend, invalid-traffic claims, beacon fires, campaign delivery, brand-safety flags, third-party vendor charges, or any indirect or consequential loss, whether in contract, tort, or otherwise, arising from use of the tools or from our handling of a submitted tag. Aggregate liability for all claims relating to the free hosted tools is limited to the greater of fees you paid us for those tools (currently none) or one hundred US dollars.

Indemnity

You will defend and indemnify the operator of vastlint.org, and people working on it, against claims, damages, and costs (including reasonable legal fees) that arise from a tag you submitted, from URLs in that tag being requested, or from your breach of these terms, including claims by your employer, a demand partner, an SSP, a DSP, a publisher, or a measurement vendor.

Changes

We may update these terms. The updated text applies to tags submitted after it is posted. Continued use of the tools after a change is acceptance of the new terms.

Contact

Questions: [email protected].