Free Online VAST Tag Tester
Paste a VAST URL or XML into the editor to preview the ad creative, inspect tracking vendors, click URLs, and inconsistencies — plus full VAST validator results against 118 IAB spec rules. VAST 2.0–4.3 supported. Nothing is stored.
URL pasteCreative previewTracking vendorsClick URLsInconsistency detection118 IAB rulesVAST 2.0–4.3Free & private
Drop a .xml file or URL · paste XML or a URL · auto-validates · ⌘↵ to validate now
Drop a .xml file or URL · paste XML or a URL · auto-validates · ⌘↵ to validate now
118
rules
6
VAST versions
<1ms
validation
0
data stored
How to use the VAST tag tester
- → Test a VAST URL: paste a VAST tag endpoint URL (e.g. from DV360, GAM, or your ad server) directly into the editor. The tester detects the URL, fetches the XML automatically, and runs all checks.
- → Test VAST XML directly: paste raw XML into the editor, or drag and drop a
.xmlfile. Validation runs automatically after a short delay. - → Preview the ad creative: the inspector panel below the editor shows the video player, companion banners, tracking vendors, click-through URLs, and any spec inconsistencies found in the tag.
- → VAST validator results: every issue is annotated with a rule ID, severity, and a link to the IAB spec section. Errors are actual spec violations; warnings are strong recommendations.
- → Nothing is stored or logged. The VAST XML is validated in-browser using a WebAssembly build of vastlint.
Need just the validator without the tester panels? VAST XML Validator → · VAST tag testing guide →