Setting Up Prebid Video Creatives in Google Ad Manager: A Practical Guide for Publishers

Video header bidding offers publishers more control, better yields, and improved transparency—but configuring video creatives in Google Ad Manager (GAM) with Prebid introduces challenges that can trip up even experienced ad operations teams. One key stumbling block: properly handling VAST XML caching and creative URL logic across different video ad scenarios.

This practical guide demystifies the video creative setup for Prebid environments within GAM, focusing on both instream and long-form formats. We’ll break down how cache locations work, what common missteps to avoid, and the operational details that matter most for ad ops teams.

Understanding Prebid Video Creative Flows in GAM

In a Prebid-enabled video environment, the flow from auction to ad delivery is controlled by how VAST XML is cached and referenced by GAM. Unlike display, where the creative setup is often a formality, video demands specific attention to cache URLs and variable substitution.

Typical publisher scenarios include:

– Instream (in-player) video monetization
– Long-form (OTT) video ads
– Mobile app video via Prebid Mobile

How VAST Caching Works

Each Prebid video bid includes a VAST XML response. However, most video players and ad servers require that the VAST be fetched from a URL, not directly from Prebid or the bidder. Prebid handles this by storing (caching) the VAST XML and providing a URL for GAM to call at ad serving time.

For instream or Prebid Mobile, you typically point creative URLs in GAM directly at the Prebid (or bidder-provided) cache, using dynamic macros to route the player to the right VAST asset per impression.

Configuring Video Creatives: Single vs. Multiple Cache Locations

Correct creative setup depends on whether all your bidders use the same VAST cache or if some bidders provide their own. Misconfiguration here leads to empty ads or error-prone auctions.

Single Cache Location

If all bidders cache VAST XML with Prebid Server or your configuration ensures a single cache, setup is streamlined. In GAM, create a VAST creative and set the URL to your Prebid Server cache endpoint, using macros like %%PATTERN:hb_uuid%% to dynamically reference each auction’s VAST asset.

For instream cases using ‘Send Top Price Bid,’ this macro is consistent for all bidders. With ‘Send All Bids,’ you may need bidder-specific macros (e.g., %%PATTERN:hb_uuid_BIDDERCODE%%) to resolve the correct asset for each demand partner. Double-check macro values correspond with your Prebid.js targeting setup.

For long-form video, add a prefix representing price, category, and duration (e.g., 50.00_news_30s_%%PATTERN:hb_cache_id%%), ensuring your creative targets match your line item granularity.

Multiple Cache Locations

If some bidders provide their own VAST cache, you have options:

– Starting with Prebid.js 4.28, use the ignoreBidderCacheKey option to have Prebid generate a wrapper and store all VAST in the standard cache. This simplifies creative setup, but adds one layer of VAST wrapping.
– Alternatively, set up creative-level targeting in your ad server. This requires creatives for each unique bidder/cache combo, with targeting aligned to either hb_bidder or hb_bidder_BIDDERCODE keys so each impression fetches the correct VAST asset.

GAM Implementation Steps and Common Pitfalls

Configuring video creatives in GAM has some unique operational nuances. Overlooking details here can break ad delivery or introduce subtle revenue losses.

Stepwise Setup Overview

1. In GAM, navigate to Delivery > Creatives and select the VAST creatives tab.
2. Create a new VAST creative as a ‘Redirect’ type.
3. Assign the VAST tag URL to the relevant cache location, ensuring macro alignment for each use case (instream, long-form, or multi-bidder).
4. Set the max ad duration appropriately; for long-form, this should match the duration in your targeting key.
5. Address any ‘failed fetch’ warnings—these are expected when the URL points to a server-side Prebid cache and can usually be ignored.
6. Declare any ad technology providers for privacy compliance, especially if hosting creative URLs on a third-party domain or CDN.
7. Preview and QA the creative to confirm correct ad loading and tracking.

Common Mistakes to Avoid

– Not aligning macros in the VAST URL with your Prebid.js targeting setup, leading to unfilled impressions.
– Forgetting to update cache locations when adding new bidders or switching Prebid versions.
– Overlooking GAM’s privacy requirements and not declaring tech providers, which may limit serving to some users.
– Failing to thoroughly QA creatives across devices and player environments, especially when using Send All Bids or multiple cache scenarios.

What this means for publishers

Publishers who master the nuances of Prebid video creative setup in GAM enjoy smoother auctions, higher fill, and cleaner reporting. Missteps can mean missed revenue, frequent troubleshooting cycles, and confusing errors for both ad ops and engineering teams. Getting cache locations and macro usage right from day one streamlines long-term operations—especially valuable for publishers running multi-bidder video environments or scaling long-form/OTT strategies.

Practical takeaway

Configuring Prebid video creatives in Google Ad Manager isn’t just about plugging in a URL—it requires understanding how VAST caching, targeting macros, and multi-bidder flows converge at creative setup. Double-check your targeting keys, test cache URLs in your player, and document cache logic when onboarding new bidders.

For teams handling both instream and long-form video, treat creative setup as a source of operational leverage. Standardizing macros and proactively declaring ad tech providers reduces support tickets and campaign friction.

Above all, commit to QA: preview creatives across your most common player environments before campaigns go live. This diligence pays off in fewer escalations and more predictable video revenue.