VAST Error 102: VAST version of response not supported
The player received a valid VAST document in a version it does not support — usually a modern 4.x tag hitting an old player.
Error 102 is a capability mismatch, not a broken tag. The response declares a VAST version the player was never built to handle. Legacy CTV apps and older web players frozen on VAST 2.0/3.0 are the usual reporters, receiving 4.x responses.
The reverse also happens: some strict modern players refuse versions below their minimum. Either way the XML itself may be perfectly valid.
Why error 102 happens
Ad server upgraded to VAST 4.x, players didn't
A DSP or ad server switches its default output to 4.0+ and every legacy player in the supply path starts firing 102. Common after platform migrations.
Version negotiation ignored in the ad request
Most ad servers accept a version parameter in the tag URL. If it's missing or ignored, the server returns its default version regardless of what the player supports.
Old SDKs baked into CTV or in-app inventory
Smart TV apps ship with player SDKs that never update. Inventory from those devices caps out at VAST 2.0/3.0 permanently.
How to fix VAST error 102
- 1
Identify which players report 102
Segment the error by device and app in your reporting. If it clusters on CTV or specific app versions, it's a legacy SDK ceiling, not a tag problem.
- 2
Request the right version in the tag URL
Configure the ad request to ask for the highest version the player supports. Most ad servers will downgrade the response format accordingly.
- 3
Serve a lower VAST version for legacy supply
Nearly everything expressible in 4.x has a 3.0 representation. Trafficking a 3.0 variant for old inventory recovers those impressions.
- 4
Verify the declared version matches the negotiated one
Validate the response and confirm the root version attribute is what the request asked for — misconfigured wrappers sometimes re-wrap a 3.0 ad in a 4.2 envelope.
Seeing error 102 on a live tag?
Paste the tag URL or XML — the validator resolves the full wrapper chain, validates the schema, downloads every media file, and shows exactly which stage fails.
Validate your VAST tagVAST error 102 — frequently asked questions
Which VAST version should I traffic by default?+
VAST 3.0 remains the widest-compatibility choice for open supply, while 4.x unlocks better features (mezzanine files, verification, universal ad ID). Many teams traffic 4.x with a 3.0 fallback for legacy paths.
Can a wrapper change the VAST version mid-chain?+
Yes. Each wrapper hop is its own VAST document and can declare its own version. A 2.0 player can fail on the first 4.x hop even if the final inline ad is 2.0.
Is error 102 lost revenue?+
Directly, yes — the impression was abandoned. If 102 volume is significant, version-targeted trafficking (serving 3.0 to legacy supply) usually recovers most of it.