VAST error codes / Ad type and trafficking
VAST error 204: Ad category required but not provided
Short answer: The placement required an ad category and none was supplied. Introduced in VAST 4.0.
What it means
Competitive separation or brand-safety rules required a `<Category>`, but the inline ad did not declare one.
Common causes
- `<Category>` omitted where the buyer or placement requires it
How to fix it
Add a `<Category>` with the correct `authority`. Pair with 205 when a category is present but blocked.
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
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# CLI: exits non-zero on errors, ideal for pipelines
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