VAST vs VPAID: what is the difference?

If you run video on your site or buy video ads, you will see "VAST/VPAID" in almost every integration guide. This article explains what each standard does, how they relate and what to choose today.

What is VAST?

VAST (Video Ad Serving Template) is an IAB Tech Lab standard. When a player needs an ad, it calls a VAST tag — a URL — and gets back an XML document that contains:

• the media file(s): the video creative in one or more formats and bitrates;
• the duration and, for skippable ads, when the skip button appears;
• the click-through URL;
• tracking events: impression, start, quartiles (25%, 50%, 75%), complete, click, errors.

The player plays the file and calls the tracking URLs at the right moments. That is how a preroll is counted and paid.

A minimal VAST response looks like this:

<VAST version="4.2">
  <Ad id="1">
    <InLine>
      <AdSystem>Example</AdSystem>
      <Impression><![CDATA[https://tracker.example/imp]]></Impression>
      <Creatives>
        <Creative>
          <Linear>
            <Duration>00:00:15</Duration>
            <MediaFiles>
              <MediaFile delivery="progressive" type="video/mp4" width="1280" height="720">
                <![CDATA[https://cdn.example/ad.mp4]]>
              </MediaFile>
            </MediaFiles>
          </Linear>
        </Creative>
      </Creatives>
    </InLine>
  </Ad>
</VAST>

Which VAST versions exist?

VAST 2.0 and 3.0 are still widely supported. VAST 4.x (4.0, 4.1, 4.2, 4.3) added better support for server-side ad insertion, ad verification and separation of the media file from interactive code. Most modern players accept several versions; check which one your player supports before you add a tag.

What is VPAID?

VPAID (Video Player-Ad Interface Definition) is an API between the player and the ad. Instead of a plain video file, the VAST response points to a piece of code (historically Flash, later JavaScript) that runs inside the player. That code could:

• show interactive elements such as forms or galleries;
• measure viewability and verify the placement;
• control playback of the video itself.

The flexibility came at a price: VPAID ads could be heavy, slow down the page, break on mobile and were sometimes used to hide fraudulent activity.

Why is VPAID being phased out?

The IAB Tech Lab split VPAID's two jobs into separate, safer standards:

• SIMID (Secure Interactive Media Interface Definition) for interactive creatives;
• Open Measurement (OM SDK) for viewability and verification.

Many players, ad servers and platforms have reduced or ended VPAID support, especially on mobile and connected TV. For new integrations, plain VAST with a video file (plus OM verification where needed) is the most compatible choice.

VAST vs VPAID at a glance

How do you use a VAST tag on your site?

1. Check your player. Most HTML5 players, including popular open-source ones, support VAST natively or through an ads plugin.
2. Add the tag your ad partner gives you as the ad source for preroll (and, if supported, midroll or postroll).
3. Test on desktop and mobile. Make sure the ad plays, can be skipped if configured and that the content starts afterwards.
4. Watch the numbers. Compare ad requests, impressions and errors. A high error rate usually means an incompatible creative or a player setting.

If you cannot change the player — for example, it is embedded from an external video host or CDN — a preloader can show the ad on top of the player instead. Our article on monetizing a video website compares the options.

VAST and VPAID at Wizads

Wizads delivers preroll through a VAST/VPAID tag that publishers add to their video player, and offers the preloader format for players where the tag cannot be installed. Advertisers buying video through the Wizads DSP can use the same formats.

Frequently asked questions

Is VAST the same as a video ad?

No. VAST is the "envelope" that describes the ad. The ad itself is the video file inside it.

Can a VAST tag contain another VAST tag?

Yes. A VAST response can be a "wrapper" that points to another VAST document. Too many wrappers slow loading and cause errors, so platforms limit their depth.

Where do VAST and VPAID fit in programmatic?

In programmatic video, the winning DSP usually returns VAST XML in its bid response, and the player plays it. See what is OpenRTB and our programmatic advertising guide.