CORS Compliance for 3rd party tags?

Published by: Brett Robinson , NPR (National Public Radio)
Published on: April 4, 2014

Hi Folks,

Our video player (JW Player) is requiring an update that would only allow us to run CORS-compliant VAST tags. They seem convinced that this is where the market is going, as things move away from flash toward html5.

Does anyone have experience with this? I am very hesitant to make any change that could potentially limit the types of creatives we can run, and spoke with someone at Brightroll who said they have no plans to make their tags CORS-compliant in the near future.

Any insight would be appreciated!





For Publishers using our video ad serving environment and plugins we strongly recommend to go for CORS only. Is the only way to guaranteed multiplatform support.

As mentioned by Derek, smartphones and tablets often represent more that 50% of the video views and video ads.

If your partners are not CORS compliant, you take the risk of losing a significant part of the revenue.

CORS is also part of the latest VAST IAB standard ( page 16). Any JavaScript module in order to interpretate a XML response like VAST needs CORS headers.

Many of our publishers are starting to write in their advertisement specs for agencies that only 3rd party VAST tags with CORS support are allowed.

Good luck,

Paid Member

Derek -

What about these issues / objections:

-- HTML5 video players generally are slower/provide a lower-quality experience.

--VPAID 2 (or even 1) is not supported by HTML5 implementations

Are there limitations that the industry is working through that one should know about before going all-in with HTML5 video player across the board?


I think this is a smart move especially if you are planning on delivering your video in a format that will work on ios or mobile using built in HTML5 video player object.

If publishers are not looking they should see how much traffic they have or are losing out on on ios. I would guess in most cases its about 40 to 50% number.

The inventory pool out there for flash video is going to dry up pretty quickly, in my opinion.

Projects like video.js and jw players are keeping up with the times for cross platform video delivery.

I use Live Rail delivering through Brightcove. Recently we removed everyone who wasn't CORS compliant as they are wasted calls and add unnecessary overhead on the client.


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