VAST error codes / Ad type and trafficking
VAST error 201: Expecting different linearity
Short answer: The player expected a different linearity (linear vs non-linear).
Debug this tag now
If you only have a live URL, test it first. If the failure is in the wrapper chain, inspect each hop. Validate resolved XML when you already have the response.
What your player reported
201· Media player expecting different linearity.
Wording from the IAB VAST 4.3 specification error table. Players may shorten or reformat it, but the code is the same.
What it means
The player asked for one linearity and got the other; for example, a linear video where an overlay was expected.
Common causes
- Linear creative returned for a non-linear placement
- Non-linear overlay returned where a linear video was expected
How to fix it
Align the creative linearity with the placement configuration.
VAST error codes are runtime buckets emitted by the player. They tell you where the failure happened, not which line of XML caused it. Paste the raw tag into the validator to map this code onto the exact element and rule.
Related error codes
- VAST error 200: Trafficking error
- VAST error 202: Expecting different duration
- VAST error 203: Expecting different size
Debug this tag now
Validate the XML, follow the wrapper chain, or check it in CI before launch:
# CLI: exits non-zero on errors, ideal for pipelines
vastlint check creative.xml