This module allows Prebid.js to support FLEDGE by integrating it with GPT’s experimental FLEDGE support.

To learn more about FLEDGE in general, go here.

This document covers the steps necessary for publishers to enable FLEDGE on their inventory. It also describes the changes Bid Adapters need to implement in order to support FLEDGE.

Publisher Integration

Publishers wishing to enable FLEDGE support must do two things. First, they must compile Prebid.js with support for this module. This is accomplished by adding the fledgeForGpt module to the list of modules they are already using:

gulp build --modules=fledgeForGpt,...

Second, they must enable FLEDGE in their Prebid.js configuration. To provide a high degree of flexiblity for testing, FLEDGE settings exist at the module level, the bidder level, and the adunit level.

Module Configuration

This module exposes the following settings:

Name Type Description Notes
enabled Boolean Enable/disable the module Defaults to false

As noted above, FLEDGE support is disabled by default. To enable it, set the enabled value to true for this module using the setConfig method of Prebid.js:

pbjs.que.push(function() {
    fledgeForGpt: {
      enabled: true

Bidder Configuration

This module adds the following setting for bidders:

Name Type Description Notes
fledgeEnabled Boolean Enable/disable a bidder to participate in FLEDGE Defaults to false

In addition to enabling FLEDGE at the module level, individual bidders must also be enabled. This allows publishers to selectively test with one or more bidders as they desire. To enable one or more bidders, use the setBidderConfig method of Prebid.js:

    bidders: ["openx"],
    config: {
        fledgeEnabled: true

AdUnit Configuration

Enabling an adunit for FLEDGE eligibility is accomplished by setting an attribute of the ortb2Imp object for that adunit.

Name Type Description Notes
ortb2Imp.ext.ae Integer Auction Environment: 1 indicates FLEDGE eligible, 0 indicates it is not Absence indicates this is not FLEDGE eligible

The ae field stands for Auction Environment and was chosen to be consistent with the field that GAM passes to bidders in their Open Bidding and Exchange Bidding APIs. More details on that can be found here In practice, this looks as follows:

    code: "my-adunit-div",
    // other config here
    ortb2Imp: {
        ext: {
            ae: 1

Bid Adapter Integration

Chrome has enabled a two-tier auction in FLEDGE. This allows multiple sellers (frequently SSPs) to act on behalf of the publisher with a single entity serving as the final decision maker. In their current approach, GPT has opted to run the final auction layer while allowing other SSPs/sellers to participate as Component Auctions which feed their bids to the final layer. To learn more about Component Auctions, go here.

The FLEDGE auction, including Component Auctions, are configured via an AuctionConfig object that defines the parameters of the auction for a given seller. This module enables FLEDGE support by allowing bid adaptors to return AuctionConfig objects in addition to bids. If a bid adaptor returns an AuctionConfig object, Prebid.js will register it with the appropriate GPT ad slot so the bidder can participate as a Component Auction in the overall FLEDGE auction for that slot. More details on the GPT API can be found here.

Modifying a bid adapter to support FLEDGE is a straightforward process and consists of the following steps:

  1. Detecting when a bid request is FLEDGE eligible
  2. Responding with AuctionConfig

FLEDGE eligibility is made available to bid adapters through the bidderRequest.fledgeEnabled field. The bidderRequest object is passed to the buildRequests method of an adapter. Bid adapters who wish to participate should read this flag and pass it to their server. FLEDGE eligibility depends on a number of parameters:

  1. Chrome enablement
  2. Publisher participatipon in the Origin Trial
  3. Publisher Prebid.js configuration (detailed above)

When a bid request is FLEDGE enabled, a bid adapter can return a tuple consisting of bids and AuctionConfig objects rather than just a list of bids:

function interpretResponse(resp, req) {
    // Load the bids from the response - this is adapter specific
    const bids = parseBids(resp);

    // Load the auctionConfigs from the response - also adapter specific
    const auctionConfigs = parseAuctionConfigs(resp);

    if (auctionConfigs) {
        // Return a tuple of bids and auctionConfigs. It is possible that bids could be null.
        return {bids, auctionConfigs};
    } else {
        return bids;

An AuctionConfig must be associated with an adunit and auction, and this is accomplished using the value in the bidId field from the objects in the validBidRequests array passed to the buildRequests function - see here for more details. This means that the AuctionConfig objects returned from interpretResponse must contain a bidId field whose value corresponds to the request it should be associated with. This may raise the question: why isn’t the AuctionConfig object returned as part of the bid? The answer is that it’s possible to participate in the FLEDGE auction without returning a contextual bid.

An example of this can be seen in the OpenX OpenRTB bid adapter here.

Other than the addition of the bidId field, the AuctionConfig object should adhere to the requirements set forth in FLEDGE. The details of creating an AuctionConfig object are beyond the scope of this document.