VAST Tag Validator
Parse, inspect, and validate VAST 2.0 through 4.2 video ad tags. Every MediaFile URL fetched, every tracking pixel tested, every companion ad inspected — all in seconds, free, with no signup.
Validate a VAST Tag →What the VAST Validator checks
VAST version compliance
Detects 2.0, 3.0, 4.0, 4.1, 4.2 and flags deprecated or non-compliant elements for each.
MediaFile validation
Fetches media within safety limits and compares available measurements with declared properties. Unavailable measurements remain unverified.
Tracking pixel tests
Declared impression, event, click and error URLs are inspected without firing them. Controlled playback records local sentinel events.
Companion ads
Companion creative references parsed, dimensions validated, and StaticResource / IFrameResource / HTMLResource checked.
Wrapper chains
Follows VAST wrappers up to standard depth, detects redirect loops, and reports chain hop count.
OMID / VPAID signals
Detects Open Measurement verification scripts and VPAID JS interfaces in the ad response.
How it works
Paste your VAST tag URL or XML
Works with ad server VAST URLs, inline VAST XML, or wrapped VAST chains.
Tag is parsed and fetched
We parse the XML, follow supported wrappers and fetch bounded media files. Declared tracker URLs are inspected offline. Fetching VAST and media still contacts their hosts.
Full report in seconds
Get VAST version, duration, MediaFile count, pixel inventory, wrapper depth, and every issue we detected.
Frequently asked questions
Which VAST versions do you support?
All major versions — VAST 2.0, 3.0, 4.0, 4.1, and 4.2. Version-specific compliance rules are applied per tag.
Does it validate MediaFile URLs?
Media files are fetched within file, byte and time limits. The report separates measured failures from unavailable or skipped measurements.
Are tracking pixels tested?
Declared tracking URLs are checked offline for syntax and HTTPS. They are not fired to prove reachability. See scan traffic details.