Companion types value 3 means iframe Resource
Iframe resource: a URL the player loads into an iframe to render the companion.
When to send it
Send 3 when the companion slot can load a URL into an iframe. The companion content is fetched from the buyer's server at render time rather than embedded in the VAST document.
Buyers choose 3 when the companion needs its own document context or must be generated when it is shown. Players without a browser engine cannot support it. It is confused with 2: both end up as HTML, but 3 is loaded from its own URL in its own frame.
Example
{
"imp": [
{
"audio": {
"companiontype": [
3
]
}
}
]
}Fields that carry it
Other values in companion types
The companion types list page explains the whole list and its common mistakes.