VAST error codes are numeric codes that CTV apps fire to the ad server's error tracking URL when an ad fails to load or play. Reading them correctly is the fastest way to diagnose delivery problems in CTV campaigns.
The most common codes in India CTV:
- 100 — XML parsing error: The VAST XML response is malformed and the player cannot parse it. Usually a DSP or ad server formatting bug. Fix: pull the raw VAST URL and validate the XML.
- 200 — Trafficking error: The VAST response is valid but the ad does not match what was requested — for example, a 30-second creative in a 15-second slot, or a skippable ad in a non-skippable unit. Fix: check creative duration and skip settings against the publisher's unit specs.
- 303 — Wrapper limit reached: The VAST response contains too many redirect wrappers (typically the limit is 5 hops). Each hop adds latency; deep chains also increase the chance of a timeout before the media file is reached. In India CTV, a 4-layer chain (DSP → verification vendor → DSP creative server → CDN) is common and sits right at the edge. Fix: ask your DSP to flatten the VAST chain, or pre-cache creatives closer to the serving endpoint.
- 401 — Media file not found: The video file URL in the VAST response returns a 404 or is unreachable. Fix: verify the creative CDN URL is live and publicly accessible without authentication.
- 402 — Media file timeout: The video file loaded too slowly for the player's timeout window (typically 5–10 seconds). Common on India mobile broadband connections with variable latency. Fix: host creative files on a CDN with India PoPs (AWS Mumbai, Cloudflare India) and use appropriate bitrates (2–5 Mbps for 1080p CTV).
- 405 — VPAID not supported: The VAST response contains a VPAID JavaScript executable, but the CTV player does not execute JavaScript. VPAID is a desktop/mobile technology that does not work on native CTV apps. Fix: ensure your DSP serves VAST-only creatives, not VPAID, for CTV line items. This is a common misconfiguration when web campaigns are extended to CTV without separate creative specs.
On India CTV, 303 (wrapper chain) and 402 (timeout) are the two highest-volume error codes. If your campaign's impression delivery is lower than bid wins suggest, check these two codes first in your DSP's VAST error reporting.
Related questions
For the full VAST technical reference, see the VAST in CTV knowledge base article.