VAST Tag Tester

Paste a VAST response or fetch a tag URL. Inspect structure, MediaFiles, and tracking before you wire the tag into a FAST channel.

VAST XML

Or fetch a VAST tag URL

Many ad servers block browser fetches (CORS). If fetch fails, open the URL in a new tab, copy the XML, and paste it above.

What this checks

VAST root and version: Confirms a <VAST> document and reads the version attribute
Inline vs Wrapper: Counts ads and flags missing VASTAdTagURI on wrappers
Linear creatives: Duration, MediaFiles (type, bitrate, size, delivery), ClickThrough, TrackingEvents
Companions and Error URLs: Surfaces companion ads and error beacons when present
Common warnings: Empty MediaFile, missing tracking, HTTP media on an HTTPS page

Runs entirely in your browser. Soft structural checks only. Not a full IAB VAST XSD certification.