Prebid.js Native Implementation Guide

• Overview
• 1. Set up your ad server ad slot and HTML div
• 2. Determine where the native template will be defined
• 3. Prebid.js Native AdUnit Overview
  • 3.1. Prebid.js and the ORTB asset fields
    • 3.1.1. Title Asset
    • 3.1.2. Image Asset
    • 3.1.3. Data Asset
  • 3.2. Custom native assets
• 4. Implementing the Native Template
  • 4.1. Implementing AdServer-Defined Template
    • 4.1.1. Turn Targeting Keys off in Prebid.js
    • 4.1.2. Create the Native Template in the Ad Server
  • 4.2. Implementing an AdUnit-Defined Template
    • 4.2.1. Prebid.js AdUnit Setup
    • 4.2.2. Define the AdServer Creative
  • 4.3. Implementing the Custom Renderer Scenario
    • 4.3.1. Prebid.js AdUnit Setup
    • 4.3.2. Define the AdServer Creative
    • 4.3.3. Define the Render JavaScript
• 5. Technical Details
• 6. Event tracking
  • 6.1. Impression Tracking
  • 6.2 Click tracking
• 7. Ad Server Implementation Details
• Further Reading

Overview

A native ad is a collection of ‘assets’ such as title, description, and image that are plugged into a publisher-defined HTML template. The template includes placeholder macros for those assets, and may be styled to match the form of the surrounding page.

At a high level, here’s now native ads work in Prebid.js:

• The publisher establishes one or more native rendering templates
• The publisher defines which AdUnits are eligible for native ads and the bidders participating in the auction.
• Prebid.js requests native demand from bidder adapters that support the “native” mediatype.
• Native bids are stored in the Prebid.js memory space.
• The call to the ad server is made as usual.
• If the native ad wins, it’s displayed and any trackers are fired.

To determine whether a bidder can supply native demand, check the bidder parameter page.

1. Set up your ad server ad slot and HTML div

Create your ad server in-page implementation as usual. See Setting Up Prebid Native in GAM for instructions for how to do this with Google Ad Manager.

There’s no reason you couldn’t use Prebid native ads with other ad servers, but we don’t have any instructions handy. Ad server vendors are welcome to submit documentation.

2. Determine where the native template will be defined

There are three options for defining the native template:

• If you want to manage your creative within the ad server (e.g. Google Ad Manager), follow the instructions for AdServer-Defined Template.
• If you’d prefer to manage your creative within the Prebid.js AdUnit, follow the instructions for AdUnit-Defined Template.
• If you’d prefer to manage your creative from a separate piece of JavaScript, follow the instructions for the Custom Renderer.

This table summarizes how the 3 approaches work:

Table 1: Native Implementation Approaches

3. Prebid.js Native AdUnit Overview

The Prebid.js AdUnit needs to define a native mediatype object to tell bidders which assets are required. This table defines all attributes that could be included in AdUnit.mediatypes.native.

Table 2: Prebid.js AdUnit Native MediaType Options

3.1. Prebid.js and the ORTB asset fields

Prebid.js supports most assets defined by the OpenRTB native 1.2 specification. The exception is ‘video’, which could be passed through to bidders, but cannot currently be rendered.

As a gentle introduction to the OpenRTB in Prebid: a request object is a javascript object that contains some well-defined properties, like

{
    native: {
        ...
        ortb: {
            assets: [...],
            eventtrackers: [...]
        }
    }
}

assets are the components of the ad that will assembled using the template. An asset must have an id, used for matching the request with the response.

Each asset should have one of the following properties:

3.1.1. Title Asset

This is a regular title and the most important property is len, to specify the length. Here’s an example:

{
    id: 2,
    required: 1,
    title: {
        len: 80
    }
},

3.1.2. Image Asset

Contains an image request. Images can be of type 1 (Icon) or 3 (Main image). There are several ways to specify the image size or aspect ratio; the OpenRTB spec contains all the possibilities. Here’s an example:

{
    id: 1,
    required: 1,
    img: {
        type: 3,
        w: 150,
        h: 50
    }
}

3.1.3. Data Asset

A ‘data’ asset is a ‘misc’ component like “sponsored by”, “rating”, likes”, or other fields that have been standardized in OpenRTB 1.2. Each data asset has a type, and based on that type the bidders will respond with the appropriate data. For example, you can request for the name of the sponsoring company by using the type 1.

Here’s an example:

{
    id: 3,
    required: 1,
    data: {
        type: 1
    }
},

For reference, this is the table that specifies all data types:

Please consult the OpenRTB Native spec for more details.

3.2. Custom native assets

In order to fit special bidder requirements, publisher can utilize various ext objects provided by OpenRTB specs.

Bid adapters will declare which custom assets they support in their documentation.

Note: The native.js::renderNativeAd() function must be called with requestAllAssets: true.

In the native template, simply access the custom value with the normal Prebid ##macro## format assuming hb_native_asset_id_ as the prefix. For example, if your custom asset has id: 7:

<div id="mytemplate">
  ... render a lovely creative ...
  ... refer to ##hb_native_asset_id_7## when appropriate ...
</div>

4. Implementing the Native Template

• If you want to manage your creative within the ad server (e.g. Google Ad Manager), follow the instructions for AdServer-Defined Creative.
• If you’d prefer to manage your creative within the Prebid.js AdUnit, follow the instructions for AdUnit-Defined Creative.
• If you’d prefer to manage your creative from a separate piece of JavaScript, follow the instructions for the Custom Renderer.

For instructions on implementing the native template within Google Ad Manager, see GAM Step by Step - Native Creative

4.1. Implementing AdServer-Defined Template

In this scenario, the body of the native creative template is managed within the ad server and includes special Prebid.js macros.

4.1.1. Turn Targeting Keys off in Prebid.js

When the native AdUnit is defined in the page, declare sendTargetingKeys: false in the native Object. This will prevent Prebid.js from sending all the native-related ad server targeting variables.

Example Native AdUnit:

pbjs.addAdUnits({
    code: slot.code,
    mediaTypes: {
        native: {
            sendTargetingKeys: false,
            ortb: {
                assets: [{
                    id: 1,
                    required: 1,
                    img: {
                        type: 3,
                        w: 150,
                        h: 50,
                    }
                },
                {
                    id: 2,
                    required: 1,
                    title: {
                        len: 80
                    }
                },
                {
                    id: 3,
                    required: 1,
                    data: {
                        type: 1
                    }
                },
                {
                    id: 4,
                    required: 1,
                    data: {
                        type: 2
                    }
                },
                {
                    id: 6,
                    required: 1,
                    img: {
                        type: 1,
                        w: 50,
                        h: 50,
                    }
                }]
            }
        }
    },
    bids: [{
        ...
    }]
});

4.1.2. Create the Native Template in the Ad Server

There are three key aspects of the native template:

1. Build the creative with special Prebid.js macros, e.g. ##hb_native_asset_id_{id}##. Note that macros can be placed in the body (HTML) and/or head (CSS) of the native creative.
2. Load the Prebid.js native rendering code. You may utilize the jsdelivr version of native.js or host your own copy. If you use the version hosted on jsdelivr, make sure any necessary ad server permissions are established.
3. Invoke the Prebid.js native rendering function with an object containing the following attributes:
   1. adid - used to identify which Prebid.js creative holds the appropriate native assets
   2. pubUrl - the URL of the page, which is needed for the HTML postmessage call
   3. requestAllAssets - tells the renderer to get all the native assets from Prebid.js rather than having to scan the template to find which specific assets are needed.

Example creative HTML:

<div class="sponsored-post">
  <div class="thumbnail" style="background-image: url(##hb_native_asset_id_1##);"></div>
  <div class="content">
    <h1><a href="%%CLICK_URL_UNESC%%##hb_native_linkurl##" target="_blank" class="pb-click" hb_native_asset_id="2">##hb_native_asset_id_2##</a></h1>
    <p>##hb_native_asset_id_4##</p>
    <div class="attribution">##hb_native_asset_id_3##</div>
  </div>
</div>
<script src="https://cdn.jsdelivr.net/npm/prebid-universal-creative@latest/dist/%%PATTERN:hb_format%%.js"></script>
<script>
    var pbNativeTagData = {};
    pbNativeTagData.pubUrl = "%%PATTERN:url%%";     // GAM specific
    pbNativeTagData.adId = "%%PATTERN:hb_adid%%";   // GAM specific
    // if you're using 'Send All Bids' mode, you should use %%PATTERN:hb_adid_BIDDER%%
    pbNativeTagData.requestAllAssets = true;
    window.pbNativeTag.renderNativeAd(pbNativeTagData);
</script>

When using ‘Send All Bids’ mode you should update pbNativeTagData.adId = "%%PATTERN:hb_adid_BIDDERCODE%%"; for each bidder’s creative.

Note the URL to the Prebid Universal Creative shown in this example uses the format where %%PATTERN:hb_format%% resolves to load native.js instead of banner.js or video.js.

Example CSS:

.sponsored-post {
    background-color: #fffdeb;
    font-family: sans-serif;
    padding: 10px 20px 10px 20px;
}

.content {
    overflow: hidden;
}

.thumbnail {
    width: 120px;
    height: 100px;
    float: left;
    margin: 0 20px 10px 0;
    background-image: url(##native_image##);
    background-size: cover;
}

h1 {
    font-size: 18px;
    margin: 0;
}

a {
    color: #0086b3;
    text-decoration: none;
}

{: .alert.alert-info :}
See [Managing the Native Template in GAM](/adops/gam-native.html#managing-the-native-template-in-gam) for ad server instructions.

.attribution {
    color: #fff;
    font-size: 9px;
    font-weight: bold;
    display: inline-block;
    letter-spacing: 2px;
    background-color: #ffd724;
    border-radius: 2px;
    padding: 4px;
}

4.2. Implementing an AdUnit-Defined Template

In this scenario, the body of the native creative template is managed within the Prebid.js AdUnit and includes special Prebid.js macros.

4.2.1. Prebid.js AdUnit Setup

When the Native AdUnit is defined in the page:

• Declare sendTargetingKeys: false in the native Object. This will prevent Prebid.js from sending all the native-related ad server targeting variables.
• Define the adTemplate as an escaped ES5 string using Prebid.js ##macros##. (See the appendix for an exhaustive list of assets and macros.) Note that this approach only affects the HTML body. Any CSS definitions need to be defined in the body of the template or in the AdServer.

Example AdUnit:

var adUnits = [{
      code: 'native-div',
      mediaTypes: {
          native: {
	    sendTargetingKeys: false,
            adTemplate: `<div class="sponsored-post">
                <div class="thumbnail" style="background-image: url(##hb_native_asset_id_1##);"></div>
                <div class="content">
                    <h1>
                        <a href="%%CLICK_URL_UNESC%%##hb_native_linkurl##" target="_blank" class="pb-click" hb_native_asset_id="2">##hb_native_asset_id_2##</a>
                    </h1>
                    <p>##hb_native_asset_id_4##</p>
                    <div class="attribution">##hb_native_asset_id_3##</div>
                </div>
            </div>`,
            ortb: {
                assets: [
                    {
                        id: 1,
                        required: 1,
                        img: {
                            type: 3,
                            w: 989,
                            h: 742,
                        }
                    }
                    {
                        id: 2,
                        required: 1,
                        title: {
                            len: 800,
                        }
                    },
                    {
                        id: 3,
                        required: true,
                        data: {
                            type: 1
                        }
                    },
                    {
                        id: 4,
                        required: true,
                        data: {
                            type: 2
                        }
                    }
                ]
            }
          }
        }
    }
}];

4.2.2. Define the AdServer Creative

Even though the body of the native creative is defined in the AdUnit, an AdServer creative is still needed. There are two key aspects of the native creative in this scenario:

1. Load the Prebid.js native rendering code. You may utilize the jsdelivr version of native.js or host your own copy. If you use the version hosted on jsdelivr, make sure any necessary ad server permissions are established.
2. Invoke the Prebid.js native rendering function with an object containing the following attributes:
   1. adid - used to identify which Prebid.js creative holds the appropriate native assets
   2. pubUrl - the URL of the page, which is needed for the HTML postmessage call
   3. requestAllAssets - tells the renderer to get all the native assets from Prebid.js. The rendering function cannot currently scan a template defined in the AdUnit.

Example Creative HTML

<script src="https://cdn.jsdelivr.net/npm/prebid-universal-creative@latest/dist//%%PATTERN:hb_format%%.js"></script>
<script>
    var pbNativeTagData = {};
    pbNativeTagData.pubUrl = "%%PATTERN:url%%";     // GAM specific
    pbNativeTagData.adId = "%%PATTERN:hb_adid%%";   // GAM specific
    // if you're using 'Send All Bids' mode, you should use %%PATTERN:hb_adid_BIDDER%%
    pbNativeTagData.requestAllAssets = true;
    // if you want to track clicks in GAM, add the following variable
    pbNativeTagData.clickUrlUnesc = "%%CLICK_URL_UNESC%%";
    window.pbNativeTag.renderNativeAd(pbNativeTagData);
</script>

When using ‘Send All Bids’ mode you should update pbNativeTagData.adId = "%%PATTERN:hb_adid_BIDDERCODE%%"; for each bidder’s creative.

See Managing the Native Template Outside of GAM for ad server instructions.

4.3. Implementing the Custom Renderer Scenario

In this scenario, the body of the native creative is managed from an external JavaScript file.

4.3.1. Prebid.js AdUnit Setup

When the Native AdUnit is defined in the page:

• DeclaresendTargetingKeys: false in the Native Object. This will prevent Prebid.js from sending all the native-related ad server targeting variables.
• Define the rendererUrl as a URL that defines a window.renderAd function in the creative iframe. The html returned by the window.renderAd function will be attached to the creative’s DOM.

Example AdUnit setup:

var adUnits = [{
      code: 'native-div',
      mediaTypes: {
          native: {
	    sendTargetingKeys: false,
            rendererUrl: "https://files.prebid.org/creatives/nativeRenderFunction.js",
            ortb: {
                assets: [{
                        id: 1,
                        required: 1,
                        img: {
                            type: 3,
                            w: 989,
                            h: 742,
                        }
                    },
                    {
                        id: 2,
                        required: 1,
                        title: {
                            len: 800,
                        }
                    },
                    {
                        id: 3,
                        required: true,
                        data: {
                            type: 1
                        }
                    },
                    {
                        id: 4,
                        required: true,
                        data: {
                            type: 2
                        }
                    }
                ]
            }
          }
        }
    }
}];

4.3.2. Define the AdServer Creative

Even though the body of the native creative is defined in the external JavaScript, an AdServer creative is still needed. There are two key aspects of the native creative in this scenario:

1. Load the Prebid.js native rendering code. You may utilize the jsdelivr version of native.js or host your own copy. If you use the version hosted on jsdelivr, make sure any necessary ad server permissions are established.
2. Invoke the Prebid.js native rendering function with an object containing the following attributes:
   1. adid - used to identify which Prebid.js creative holds the appropriate native assets
   2. pubUrl - the URL of the page, which is needed for the HTML postmessage call
   3. requestAllAssets - tells the renderer to get all the native assets from Prebid.js so they can be passed to the render function.

Example creative HTML:

<script src="https://cdn.jsdelivr.net/npm/prebid-universal-creative@latest/dist//%%PATTERN:hb_format%%.js"></script>
<script>
    var pbNativeTagData = {};
    pbNativeTagData.pubUrl = "%%PATTERN:url%%";    // GAM specific
    pbNativeTagData.adId = "%%PATTERN:hb_adid%%";  // GAM specific
    // if you're using 'Send All Bids' mode, you should use %%PATTERN:hb_adid_BIDDER%%
    pbNativeTagData.requestAllAssets = true;
    // if you want to track clicks in GAM, add the following variable
    pbNativeTagData.clickUrlUnesc = "%%CLICK_URL_UNESC%%";
    window.pbNativeTag.renderNativeAd(pbNativeTagData);
</script>

When using Send All Bids you should update pbNativeTagData.adId = "%%PATTERN:hb_adid_biddercode%%"; for each bidder’s creative

See Managing the Native Template Outside of GAM for ad server instructions.

4.3.3. Define the Render JavaScript

Requirements for a native rendering function:

• It must define a window.renderAd() function that will be called by the Prebid Universal Creative
• The renderAd() function is passed an object containing an ortb property that contains the response in OpenRTB format, and must return a fully resolved and ready-to-display block of HTML that will be appended to the body.
• The renderer can optionally expose a window.postRenderAd() function that can be useful to trigger javascript functions.

Here’s an example script:

window.renderAd = function(bid) {
    const { ortb } = bid;
	let template = `
    <div class="sponsored-post">
        <div class="thumbnail" style="background-image: url(##hb_native_asset_id_1##);"></div>
        <div class="content">
            <h1>
                <a href="%%CLICK_URL_UNESC%%##hb_native_linkurl##" target="_blank" class="pb-click" hb_native_asset_id="2">
                ##hb_native_asset_id_2##
                </a>
            </h1>
            <p>##hb_native_asset_id_4##</p>
            <div class="attribution">##hb_native_asset_id_3##</div>
        </div>
    </div>`;

    const getAssetValue = (asset) => {
        if (asset.img) {
            return asset.img.url;
        }
        if (asset.data) {
            return asset.data.value;
        }
        if (asset.title) {
            return asset.title.text;
        }
        if (asset.video) {
            return asset.video.vasttag;
        }
    }

    ortb.assets.forEach(asset => {
        template = template.replace(`##hb_native_asset_id_${asset.id}##`, getAssetValue(asset));
    });

    if (ortb.privacy) {
        template = template.replace("##hb_native_privacy##", ortb.privacy);
    }
    template = template.replace("##hb_native_linkurl##", ortb.link.url);
	return template;
}

window.postRenderAd(bid) {
    console.log('Native ad has been attached to the DOM');
    // again, the ortb is in bid.ortb
    ...
}

Note that the format of any macros in external render JavaScript is totally up to you. The data object coming is in OpenRTB format.

5. Technical Details

A few details that may help understand and debug your setup:

1. The system assumes that native creatives will be wrapped in an iframe.
2. The native assets are stored in the Prebid.js memory space as the original OpenRTB response.
3. When the window.pbNativeTag.renderNativeAd() function is called, an HTML5 postmessage is made. Prebid.js is listening for this message, and responds with the bidder’s OpenRTB assets.
4. If the template was defined in the AdServer, the body of the iframe will be replaced. Otherwise, if the template was defined in the AdUnit or external JavaScript, the body of the iframe will be appended with resolved creative HTML.
5. If the AdServer supports it, CSS styles can be defined in the iframe head. Otherwise, they must be defined in the body of the template, for example with
6. Note that native iframes will be resized to the height of the creative after render.

6. Event tracking

Native ads support 3 different types of event tracking:

• impression tracking
• click tracking
• viewability tracking

6.1. Impression Tracking

Prebid supports both methods (img and js) for impression tracking. Publishers just need to specify which method is support for which adUnit. This is configured in adUnit.mediaTypes.native.ortb.eventtrackers. For more details take a look at the OpenRTB spec.

How impression tracking works step by step:

• When the window.pbNativeTag.renderNativeAd() is called, the Prebid Universal Creative will request OpenRTB response from Prebid.js (via postmessage).
• Prebid.js responds with OpenRTB response that contains eventtrackers
• When the Prebid Universal Creative renders the native ad, it will gather all impression trackers from the response and for each tracker it will:
  • if tracker is img method, Prebid Universal Creative will fire pixel provided in the url property
  • if tracker is js method, Prebid Universal Creative will load the script in the same iframe where native ad is rendered

The publisher doesn’t need to implement anything for impression tracking to work, all that is needed is proper configuration of OpenRTB request on adUnit level. Prebid.js + Prebid Universal Creative will automatically take care of the impression tracking.

6.2 Click tracking

According to the [OpenRTB spec](https://www.iab.com/wp-content/uploads/2018/03/OpenRTB-Native-Ads-Specification-Final-1.2.pdf], click trackers can be found in link objects. There is ‘master’ link object for the entire native ad and also each asset in the response can have it’s own separate link object.

When native ad is rendered prebid universal creative will attach click listeners on all DOM elements that have class pb-click. Which means it’s up to the publisher to decide which DOM objects are ‘clickable’.

Furthermore, prebid universal creative can also track if some specific asset is clicked. To enable this, publisher needs to assign custom attribute to associated DOM element: hb_native_asset_id="5". In that case if user clicks on asset with id: 5 prebid universal creative will take link object from that asset and fire all click trackers. If asset doesn’t have link object, prebid universal creative will fire all click trackers associated with ‘master’ link object (as described in openRTB specs).

<div class="pb-click" hb_native_asset_id="5">

If the user clicks on this div, the Prebid Universal Creative will take the link object from the identified asset and fire any click trackers. If the asset doesn’t have a link object, it will just fire the click trackers associated with ‘master’ link object.

Example of how to configure a template so that the Prebid Universal Creative can fire click trackers:

<div class="sponsored-post">
  <div class="thumbnail" style="background-image: url(##hb_native_asset_id_1##);"></div>
  <div class="content">
    <h1><a href="%%CLICK_URL_UNESC%%##hb_native_linkurl##" target="_blank" class="pb-click" hb_native_asset_id="2">##hb_native_asset_id_2##</a></h1>
    <p class="pb-click" hb_native_asset_id="4">##hb_native_asset_id_4##</p>
    <div class="attribution" class="pb-click" hb_native_asset_id="3">##hb_native_asset_id_3##</div>
  </div>
</div>

7. Ad Server Implementation Details

There are detailed instructions for setting up native in GAM, but none of the Prebid functionality is specific to GAM. The requirements to use any of these approaches in a different ad server are:

1. Put the creative in an iframe and load native.js
2. Invoke the renderNativeAd() function with a hash that includes the following values:
   1. pbNativeTagData.pubUrl = “PAGE URL”;
   2. pbNativeTagData.adId = “PREBID ADID”;
   3. pbNativeTagData.requestAllAssets = true;
3. renderNativeAd() will look for the existence of an “adTemplate” value in the AdUnit. If it finds one, it will resolve macros and append it to the iframe’s body.
4. Otherwise, renderNativeAd() will look for the existence of a “rendererUrl” value in the AdUnit. If it finds one, it loads the script then calls window.renderAd() and appends the results to the iframe’s body.
5. Otherwise renderNativeAd() scans the iframe body and resolves macros.

Further Reading

• Prebid Native Format
• Setting Up Prebid Native in GAM