Is there any harm in having multiple CDN-links in banner ad?

[SeriuosBusiness]

Hey!

I was wondering if there's any harm in having multiple CDN-links in a banner? I prefer fetching GSAP's library from mdn's CDN due to our client's specs but since it's hosted on Google's servers, it might get blocked by some privacy settings.
So could I circumvent this by just having two CDN-links in my banners? The network impact should be pretty minimal so that at least shouldn't be a problem?

Like so:
<script src="https://s0.2mdn.net/ads/studio/cached_libs/gsap_3.5.1_min.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.6.0/gsap.min.js"></script>

Thanks!

[davi]

Personally, I would ask the media team/traffickers/sites what commonly used shared libraries are allowed and then, specifically, if you can use more than one and if they can come from the domains you mentioned. IMHO, the stuff out there is outdated.
 

Perhaps other people can add to this, but as far as documentation goes (and this may have been updated), here’s what I have:

 

1) IAB’s new ad portfolio from 2017 (page 16 under ’Shared Libraries and Resources’), states the following:

"Browser caching capabilities benefit all parties by eliminating the need to download previously requested resources that already exist on the user’s device. Advertisers (Creative developers) are encouraged to take advantage of browser caching functionality by linking to shared libraries hosted on the Ad Serving party’s (Publisher ad server or third-party ad server) domain that are used across campaigns.

Please refer to the IAB HTML5 Resources wiki for commonly used shared libraries and check with the ad serving party for the ones that are hosted.

Publishers and first-party ad servers should specify the shared library name(s) and originating CDN url(s) that are exempt and can be excluded from file weight calculations in their ad specifications and guidance to advertisers. They must provide reasonable notice for the advertiser to update creative.

Shared libraries that are exempt are allowed a combined maximum of 50 kB file weight (gzipped) as part of initial load. No limit is imposed during subload. Any shared library and CDN NOT specified in publisher or ad server guidance must be counted in file weight calculations submitted by advertisers.”
 

So what I take from that is, use as many as you want as long as they're in the exempt list and the combined k-weight is 50kb. I know the link to the exempt list that the IAB mentions has changed, but you can probably Google that.

 

2) Whether or not sites adhere strictly to the above is another question. In Google’s docs about this it doesn’t mention how many or if there’s a k-weight limit but does say “replace any references to common JavaScript libraries with Studio hosted URLs” (to me, that sounds like, yeah, sure, go to town. As long as it’s from us). I can’t remember if an external CDN link will pass DCM’s ad validator or get blocked. You can probably test that fairly easily though. If it wasn’t allowed to be exempt, then the file size would get counted in the initial load spec.