VAST and VPAID are the technical standards that govern how video ads are delivered to CTV devices. VAST (Video Ad Serving Template) is the dominant standard for CTV — it tells the video player where to find the ad, how long to play it, and which tracking pixels to fire. VPAID (Video Player Ad-Serving Interface Definition) is an older standard that adds interactivity and scripting to video ads — and it is being phased out on CTV because it creates security, performance, and measurement problems. Understanding both matters because they affect what you can and cannot track, what creative capabilities you have, and how your ads actually reach devices.
VAST explained
VAST is an XML-based standard created by the IAB. When a CTV video player needs to show an ad, it sends a request to the ad server. The ad server returns a VAST XML response containing: the URL of the video file to play, the ad duration, click-through URL, and a set of tracking event URLs (impression, start, firstquartile, midpoint, thirdquartile, complete, click). The player downloads the video, fires the impression pixel when playback starts, fires the quartile pixels as playback progresses, and fires the complete pixel when the ad finishes.
VAST 4.x (the current version) adds support for verification scripts, media file selection, and more granular event tracking. Most India CTV platforms operate on VAST 2.0 or VAST 3.0 — the older versions are sufficient for standard non-interactive pre-roll and mid-roll. Platform documentation on which VAST version they support should be confirmed during trafficking setup.
VAST Wrapper and VAST Redirect
A VAST Wrapper is a VAST tag that points to another VAST tag rather than directly to a video file. This is how ad serving chains work: a publisher's ad server returns a VAST Wrapper pointing to a DSP's ad server, which returns another Wrapper pointing to the advertiser's ad server, which finally returns the actual creative. Each hop adds latency.
On CTV, where buffering is visible and viewer patience for technical delays is low, long VAST chains (3+ hops) cause buffering, ad timeouts, and missed impressions. India CTV campaigns that run through multiple intermediaries sometimes fail to serve correctly because the VAST chain is too long for the platform's timeout threshold. When setting up India CTV campaigns, ask the platform for their maximum VAST redirect depth and timeout threshold — typically 2–3 seconds and 3 redirect hops.
SSAI and VAST on India CTV platforms
India's major CTV platforms — JioCinema and Hotstar — use SSAI (server-side ad insertion). With SSAI, the publisher's server stitches the ad video file directly into the content stream before it reaches the device. From the video player's perspective, there is no VAST tag to parse — just a continuous video stream. The SSAI server handles the VAST call internally.
The consequence for advertisers: client-side tracking pixels (the URLs in the VAST file that fire when quartile events happen on the device) do not fire. Your third-party verification vendor (IAS, DoubleVerify, MOAT) cannot receive client-side signals. Impression and completion tracking comes from the SSAI server's reporting, not from the creative's VAST pixels. This is why third-party viewability measurement on JioCinema and Hotstar is structurally limited — the measurement infrastructure requires client-side execution that SSAI prevents.
VPAID explained and why it is being retired
VPAID is an older standard that wraps a video ad in a JavaScript execution container. This allows the ad to be interactive — the ad itself can run scripts, capture clicks, measure attention, and communicate back to the ad server in real time. In a desktop browser, VPAID enabled rich interactive video ads. On CTV, VPAID creates serious problems.
CTV devices run native apps, not web browsers. JavaScript execution in a native CTV app environment is unreliable — devices process VPAID scripts inconsistently, causing freezes, crashes, and serving failures. Security concerns also exist: VPAID containers can execute arbitrary JavaScript, creating a vector for malicious code in the ad supply chain. The IAB and major CTV platforms have moved to deprecate VPAID on CTV.
VAST with SIMID (Secure Interactive Media Interface Definition) is the replacement standard for interactive CTV ads — it provides a secure, sandboxed environment for ad interactivity without the security and performance issues of VPAID. SIMID adoption is still in early stages in India.
What India buyers should do
For standard CTV campaigns in India: use VAST, not VPAID. Confirm platform VAST version support before trafficking. Keep VAST chains to 2 hops or fewer to avoid timeout failures. If running on JioCinema or Hotstar, accept that third-party tracking pixels will not fire client-side and plan measurement accordingly. For interactive CTV creative, check with the platform on SIMID support rather than assuming VPAID will work.