An Introduction to Pixels

A tracking pixel is a concept that has a long history on the Internet and goes by many names. Whether it is called a web beacon or page tag, the tracking pixel is an embedded object; commonly in a web page, which unobtrusively allows Publishers and Advertisers to record relevant the activity of their customers on the Internet. This information ultimately facilitates campaign performance measurement, conversion event tracking, and audience insights in the DSP.

There are three key concepts when it comes to pixels:

  • How it will be implemented

  • Where it will be implemented

  • How it will be loaded (Secure vs Non-Secure)

Each of these key concepts are covered below.

How to Implement

Pixels can be implemented directly into the HTML of the webpage by placing the pixel code exactly as it was provisioned between the <body> and </body> tags. However, if the site is using container tags (i.e. DART Floodlight or Atlas UAT) or Tag Management Platforms (i.e. Signal or Google Tag Manager) then pixels should be implemented into their respective receptacles. Containers and Tag Management Platforms typically utilize templates that facilitate the specific needs of a campaign. You may reference the Common Implementation Methods section below for screenshots of correct implementations in various systems. 

Where to Implement

In order to facilitate the correct setup, pixels should only be placed once (1x) on the pages they were designed to be placed on. For example, a coupon download pixel should only be placed once on the coupon download page, a home page pixel should be placed once on the home page, and a landing page pixel should be placed once on the landing page, etc. Most importantly, the conversion pixel should only be placed once (1x) on the intended user conversion action and nowhere else. 

Secure vs. Non-Secure

Pixels need to be loaded either securely or non-securely. Secure pixels should be used on all "https" pages and nonsecure pixels should be used on "http" pages. The main difference is that secure pixels go through an extra step of encoding information so the message being sent is only readable by the sender and intended reader of the message. Nonsecure pages can support both secure and nonsecure pixels, but secure pages can only use secure pixels. For optimal load time, we recommend that secure pixels only be used on secure pages. Zeta DSP JavaScript pixels are protocol agnostic, meaning they adjust based on the protocol of the page it is implemented on, but Image pixels will need an explicit "http" or "https" declaration.


To speed up internet browsing, individual user browsers store local copies of web pages and images that are accessed frequently. On subsequent requests for the same URL, browsers use the locally stored content to minimize data transmission and decrease load times. This is known as caching. In order to ensure accurate pixel counts, pixels need to make unique calls to the server and defeat caching, which is done by appending a constantly changing random number, called a cachebuster, into the URL, thereby making the browser believe each request is unique. Without a cachebuster there will most likely be discrepancies between first party and third party servers.

Common Implementation Methods

It is important pixels are setup correctly in order to ensure that DSP is accurately receiving data in order to optimize the campaign. Correct setup ensures that every user that loads the page will fire the DSP pixel. We recommend against using frequency capping or conditional firing rules as they may provide an incomplete understanding of your audience.

DoubleClick Floodlight

Default cachebuster macro: %n 

Additional notes about DoubleClick: 

  • Setup as a “Default” Pixel under Dynamic Tags.

    • Do not place the DSP pixel as a Publisher tag unless instructed. Placing the DSP pixel as a Publisher tag would cause the pixel to conditionally fire on an Attributed Conversion, which gives us an incomplete view of an audience.

  • Ensure Floodlight is implemented in HTML as an iFrame or global site Floodlight, not an image Floodlight.

  • Ensure the correct Floodlight is being modified. Every Floodlight can be uniquely identified by their Category ID, which is visible in the Floodlight URL as cat=

Google Tag Manager

Default cachebuster macro: {{Random Number}} 

Depending on if the GTM account is V1 or V2, use the chart below to confirm the {{Random Number}} cachebust macro is setup correctly.

Google Tag Manager Version

Access URL

To Enable {{Random Number}}


Create a new user-defined variable (macro) of type Random Number.


Activate the Random Number Built-in Variable.

Additional notes about Google Tag Manager: 

  • The Zeta DSP Pixel should be setup as a Custom HTML Tag within GTM with “support document.write” checked on.

  • Ensure firing rules (called Triggers) are correctly setup. If incorrectly setup, this can lead to unexpected conditional firing.

  • Confirm most recent changes have been published to the live container.


Default cachebust macro: [%Random%] 

Additional notes about Sizmek: 

  • Sizmek has many settings that may conditionally fire pixels (deduplication, last entry in path, etc). Please ensure all these settings are disabled.

Direct to HTML

Default cachebust macro: None

Additional notes about Direct to HTML: 

  • The default cachebuster macro is unique to each Advertiser.

  • Our pixels should go between the <body> and </body> tags.

  • Please work with your web developer to ensure pixels are implemented with best practices and guidelines in mind.

JavaScript vs Image Functionality




Page Load Performance

The Zeta DSP pixel and piggybacked pixels load asynchronously, in a non-blocking manner.

The Zeta DSP image and piggybacked pixels load asynchronously, in a blocking manner.

Cooke Matching

Higher match rate because cookie matching piggybacks load asynchronously resulting in more partner calls being completed.

Lower match rate because cookie matching piggybacks load synchronously so one partner call must complete before the next can begin.


Protocol agnostic based on the page on which it fires. Zeta DSP takes care of the secure (https) or non-secure (HTTP) automatically.

The client is responsible for properly declaring either secure (https) or non-secure (http).


Global timeout of 15 seconds.

Cookie Matching

In order to buy inventory efficiently and programmatically, the Zeta DSP utilizes pixels from our exchange partners to match their user IDs with our internal user IDs. With this cookie matching strategy, we are able to have more insight to the user's actions and determine which user is more likely to convert. This is a standard programmatic practice and an effective strategy that we have always had in place. With that being said, we do have the ability to turn off these piggybacked pixels. However, the disabling of cookie matching would negatively impact campaign performance.

Below is the current list of cookie match partners:

Partner Name

HTML Syntax

Google Adx

<img src="{base64userid}&forward=" width="1" height="1" />


<img style="display:none" src="{userid}" width="1" height="1">


<img src="{userid}&" width="1" height="1">

Yahoo Ad Exchange (Right Media)

<img src="" width="1" height="1" />

Rubicon Project

<img src="{userid}&expires=30&next=" width="1" height="1">

Index Exchange

<img src="{userid}&forward=" width="1" height="1" />


<img src="{userid}&img=1" width="1" height="1">


<img src="{userid}&redir=" border="0" width="1" height="1" />


<img src="" width="1" height="1">


<img src="{userid}&expires=30" width="1" height="1" />


<img src="{userid}" border="0" width="1" height="1" />


<img src=",000{userid}&r={timestamp}" width="1" height="1" />


<img src="{userid}" border="0" width="1" height="1" />


<img src="" width="1" height="1">

Sizmek Ad Server

<img src="" width="1" height="1">

<img src="{userid}" height="1" width="1" />


<img src="{userid}" width="1" height="1">


<img src="{userid}&_origin=1" height="1" width="1" style="display:none" />

DXH Zeta Data Cloud

<img src="{userid}" width="1" height="1" style="display: none" />


<img src="{userid}&r={cachebust}" height="1" width="1" border="0"/>

DXH Eyeota

<img src="" width="1" height="1" />


<img src="{userid}" border="0" width="1" height="1" />

DXH Semcasting

<img src="{userid}" width="1" height="1"/>