What Are the Differences Between Prebid.js and Prebid Server?

There’s more than one way to implement header bidding, but not all methods will be viable for you. Right now, two of the most popular open-source header bidding solutions are Prebid.js and Prebid Server.

While both serve a similar purpose and can be used simultaneously, they’re slightly different solutions. It’s important to understand both solutions in order to determine the best one for your needs.

What Exactly is Prebid?

Prebid refers to the open-source wrapper technology used for header bidding. It’s easy to conflate header bidding and Prebid when it comes to programmatic ad buying and selling.

Let’s simplify it:

Header bidding is the mechanism used by digital publishers to put their ad inventory up for sale on various programmatic marketplaces simultaneously. It is implemented by adding a piece of code into the header of their webpage — hence the name.

This code automatically generates requests to different ad exchanges to fetch bids for the publisher’s inventory. Then, it sends those bids along to their ad servers. Header bidding has replaced the traditional ad exchange technique known as waterfalling (or daisy-chaining). It is much more efficient in producing more advertising revenue.

Prebid is a global organization managed by volunteer community members across the ad tech industry. They collaborate to create a complete product suite of open-source header bidding solutions. As a result, any publisher can get started on their own.

The open-source wrappers are used to manage the technical process of managing ad bid requests to each ad exchange, depending on its configuration. This ensures a common “timeout” to select the highest bid return across these exchanges, returning to the ad server with the best value.

So, what’s the difference?

Header bidding is a method used by publishers to sell their ad inventory and effectively monetize their content.

You can host header bidding on the client-side, within the user’s browser. Or on the server-side, within your server (outside of the user’s browser). There is a technical element to properly implementing header bidding. This is why many ad networks offer their own managed Prebid service.

All this means is that you can leverage a third-party service to manage your website monetization stack.

However, you can create and manage your own customized header bidding experience through Prebid’s complete suite of solutions. Namely, Prebid.js (client-side header bidding) and Prebid Server (server-side header bidding).

What is Prebid.js?

Prebid.js is the open-source header bidding wrapper that helps publishers connect with multiple demand partners simultaneously on the client-side. In client-side header bidding, the auction code lives on your website and is executed within your users’ browser. This means that the browser handles the entire auction logic, including requesting and receiving the bids and selecting a winner.

Prebid.js is actually a core feature within the Prebid ecosystem as it can support multiple formats, including native, video, display, etc. It also provides publishers with a simplified process for header bidding that can be scaled to fit individual monetization needs. Additionally, it allows publishers to easily set up line items within Google Ad Manager. It’s an efficient way to send individual requests to bidding partners and manage their returns.

What are the benefits of Prebid.js?

The benefits of using a Prebid.js wrapper include the following:

  • Transparency: It runs on an open-source platform which allows anyone using it to read the code used to power each header bidding auction. This means you can see which demand partners are active and how much you’re earning for your premium ad inventories.
  • Better advertising revenue opportunities: Cookie match rates are higher with a client-side implementation because user IDs don’t need to be synced with an additional server. Advertisers will typically bid more on impressions where they can accurately identify a user. Depending on the setup, client-side header bidding can deliver more revenue for every impression.
  • It allows asynchronous ad calls to be made: Prebid.js allows for simultaneous calls to various demand partners to be made without interrupting the user experience. It does this by implementing a single timeout feature that prevents page load speeds to be affected while demand partners are returning bid responses.

What is Prebid Server?

Prebid Server is a server-side header bidding solution that runs auctions on a server rather than in the user’s browsers.

When a publisher implements Prebid Server for their server-side auction integrations, they are required to make one call to the server. It’ll respond by calling on the configured bidder adapters. The bidder who comes back with the highest bid will have their ad served on the website.

When a user lands on your website, a client (like Prebid.js) makes one call to Prebid Server. It then calls the applicable demand partners once it has determined which bidders to use. After collecting the responses from the demand partners, it returns the winning bids back to the client. From here, the winning bids are passed to the ad server. The ad server gets the final say on who had the highest bid. If Prebid had the highest bid, it will render the winning creative on your website for your user to see.

This is Prebid’s visual description of how the Prebid Server works.

One important distinction is that Prebid Server is still a server that needs someplace to run. You can use a hosted, managed solution that offers updated server software, such as Magnite, to manage requests. Or, you can create your own self-hosted server. Granted, the latter will require more planning and resources to set up.

What are the benefits of using Prebid Server?

The benefits of using Prebid Server include the following:

  • Significantly reduced latency: Arguably one of the greatest benefits of using Prebid Server is that its process is carried out using a server-side implementation. This allows a web page’s content to load independently of the actual ad auction. As such, the ads’ load speed is improved as it’s separate from the real-time auction. Resulting in a better overall user experience.
  • It allows for multiple demand partners: With server-side auctions, generating multiple ad calls is essentially obstacle-free. This gives publishers the opportunity to add even more bidders for their requests. More bidders may equate to more revenue, but client-side integrations suffer from bidder limits. With only one call to Prebid Server, publishers can add as many bidders as they’d like without worrying too much about page latency.
  • It allows for unified auctions: Rather than managing and setting up ad units individually per wrapper, publishers can use Prebid Server for all ad units to get performance reports of all their bidders in one place. Essentially, it unites both the server-side and client-side platforms in an auction.

When to choose Prebid.js or Prebid Server?

In general, the choice really comes down to how you’re looking to scale up your demand and improve your user experience.

With the help of Prebid Server, you’ll be able to add as many server-side platforms (SSPs) as you want, without having to worry about slowing down or interrupting your user experience while the ads are loading onto the page — otherwise known as latency. Additionally, with the server-side setup (compared to the client-side setup of Prebid.js) you’ll only have to send out a single request as the entire auction will take place on the server-side.

Adversely, Prebid.js has to send out multiple requests to the ad server, where the user’s browser has to handle the auction. This may negatively affect your website page load time and lower your PageSpeed Insights score. However, for publishers who do not have the resources to manage their own server solution, Prebid.js is much easier and faster to setup. Additionally, with a higher cookie match rate and a well-optimized configuration, you’ll potentially see better revenue opportunities with Prebid.js.

Ultimately, the choice depends on what resources you can allocate to either implementation.

Fun fact: Blockthrough’s proprietary technology was built by our CTO, Matt Kendall, who was also the creator of Prebid.js.

Which is better — Prebid or a managed solution?

To recap, Prebid refers to a suite of open-source header bidding products managed by a global community. This makes it rather cost-effective and offers a universal appeal for all the ad tech players who make up its community. However, it’s not the only solution regarding a more streamlined method to header bidding.

You can also go with a managed solution.

As noted previously, there are many ad networks and SSPs that offer to configure and host your Prebid implementation for you. This method is ideal for publishers who want to focus on content creation as opposed to finetuning their web monetization techniques.

Or, publishers who simply do not have the time or resources to customize their own Prebid solution.

The main caveat is that you do not control the code given to you by a third-party vendor. Depending on their setup, the tradeoff to having another service manage your header bidding experience could result in an increase in page latency on your website.

At the end of the day, if you choose to use Prebid technology, you’ll need to ensure that either you or your team is able to manage it. On the other hand, everything will be taken care of for you with a managed solution.

Originally published on BlockThrough.com

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