Back in 2015, AppNexus designed a client-side wrapper, Prebid.js. After partnering with the Rubicon Project in 2017, they, together, announcement‒an open-source header bidding solution for publishers.

Header bidding has become very popular since. However, industry people still have a hard time differentiating between Prebid.js, prebid wrapper, and header bidding wrapper.

Here, we try to clear all the confusion, starting with Prebid.js.

What is Prebid.js?

Popularly known as the prebid wrapper, Prebid.js is the most well-known Open Source header bidding wrapper. A good analogy to understand Prebid.js is the WordPress equivalent of header bidding. Just like WordPress, Prebid is open source and makes header bidding free to use and customizable according to publishers’ requirements. defines Prebid.js as, “A feature-rich header bidding platform for the web, including more than 150 demand sources and 15 analytics adapters supporting currency conversion, GDPR, common ID systems, and multiple ad servers.”

Prebid.js enables publishers to carry out header bidding on their property (site or app). It also allows publishers to set up line items, manage them effectively, make use of asynchronous ad calls and do all this without the need of developing a custom solution.

How Does Prebid.js Work?

how does prebid.js work

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Prebid.js takes only a few steps to carry out the header bidding auction. Here are those steps:

  • As soon as an impression becomes available, Prebid.js library initiates and starts fetching the bids and creatives from the respective ad exchanges, SSPs and advertisers.
  • These bids and creatives are then forwarded to ad server.
  • The ad server then uses predetermined logic including (but not limited to) floor price, ad type and format to compare these bids and stores them as line items by keeping the auction time under timeout set by the publisher.
  • After comparison, if the ad server finds a qualifying bid, it sends a signal to Prebid.js library along with the details of the winning bid and the placement of the winning creative on the webpage.

Benefits of Using Prebid Wrapper

As claimed by, header bidding auctions run faster using Prebid.js wrapper, which results in decreasing the demand partner response time and ends up providing a better user experience. Furthermore, the technology is quite flexible, works for both mobile and desktop channels including display, native, and video ad types.

The system provides analytics to understand what’s working and what (non-performing) partners to exclude from the wrapper. Moreover, Prebid has its own community of working professionals and experts who are continuously working to improve the product and provide assistance to other users. Given the ultimate goal of running ads is to make money the underlying benefit for publisher is an increase in profits using Prebid.js.

Are there any Drawbacks?

While Prebid is free and open-sourced, this doesn’t necessarily mean that anyone can easily set up, maintain, and run header bidding using it.

If you (publisher) have an ad ops team to set up, manage, and monitor the header bidding implementation, you are good to go. Else, you most likely need assistance with optimization.

Another thing to be wary of is the site loading speed. Although header bidding decreases the time lag in the response time from demand partner, the process of loading scripts to run header bidding auction on the page inevitably causes a delay on the client browser, increasing page latency.

Given the complexity of implementing and maintaining the wrapper, header bidding is not for every publisher. There are multiple factors to consider when thinking of using the Prebid.js wrapper, so it is always a better idea to test it first to determine if it is indeed the right solution for you and is in line with both the long term business and the UX goals.

Also read: What is Post-bid? Pros, Cons, and Comparison with Header Bidding

Prebid.js: FAQs for Publishers

How much does Prebid cost?

Prebid.js is free to use. However, if you are not equipped with an ad ops team having required technical knowledge to install and setup Prebid.js, then you might need to pay engineers to do that for you.

Does Prebid offer server-side compatibility?

Yes, Prebid has a server-side header bidding solution, called Prebid server. As the name suggests, the heavy lifting of the auction will be conducted on server-side, hence, improving page load time and user experience.

How many bidders should be added?

The answer to this will vary from publisher to publisher. Thus running A/B tests and collecting real data from pages running Prebid to get an answer would be the best path to take. More bidders might sound like a good idea to increase the profit (in theory, it might actually increase profit), however, it would increase page latency too, which ultimately decreases revenue.

What about Prebid support?

As Prebid is open source, there is no official support. But you can join various resourceful communities (including Slack and Reddit) to get answers to your queries.

Can Prebid track revenue and traffic source via interface?

No, Prebid does not provide an interface to track such details yet. Although, publishers can integrate Google Analytics with Prebid to get header bidding stats, however, there is no guarantee of these stats being accurate.


Shubham is a digital marketer with rich experience working in the advertisement technology industry. He has vast experience in the programmatic industry, driving business strategy and scaling functions including but not limited to growth and marketing, Operations, process optimization, and Sales.

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