Pixels vs. Postbacks: Which Tracking Method Should You Be Using?

Photo by Nesa by Makers

When it comes to performance marketing, one of the biggest questions you can ask yourself (or your advertiser) is what kind of conversion tracking protocol you want to use: pixel tracking (client-side) or postback tracking (server-side). There are benefits and disadvantages to each, and it’s important to distinguish between them if you wish to be successful. So, let’s break it down.

First — definitions:

Pixel Tracking

Also called client-side, cookie-based, in-browser tracking. This method relies on the user’s browser to track conversions by placing a cookie on the click that is called again on conversion to authenticate the session and attribute the conversion to the correct affiliate. Pixel-based offers use cookies to track because they can store the session values in the cookie, and with the way pixels are designed to track, can extract this information from the browser easily. As a result, setting up an offer to track using pixels is very simple and only involves placing the HTML offer pixel on the conversion page.

Use pixel tracking when:

TUNE’s general recommendation is to use pixel tracking as little as possible, as pixel tracking only works for non-mobile web traffic where cookies can be stored. Additionally, major browsers like Safari, Chrome, and Firefox are moving away from allowing tracking-related cookies even for first parties.

As the last resort, use pixel tracking if the following are true:

The offer’s advertiser is unable to send server-side conversion notifications.
The offer does not involve mobile app installs.
The offer’s desired end users are on browsers that support tracking-related cookies.

For more information, check out this TUNE support article explaining implementation of pixel tracking.

Postback Tracking

Also known as server-side, server call, server 2 server (or server-to-server), s2s and, mistakenly, server pixel tracking, relies on the advertiser’s servers to track sessions generated on clicks to attribute conversions.  The servers record and then pass the transaction ID back to TUNE. This method is independent of the user’s browser. Postback tracking can be thought of as two separate processes: what happens when a user clicks on an offer and what happens upon conversion.

Leading up to the conversion:

1. User sees an offer.
2. User clicks on the offer.
3. Click goes to a TUNE server. The server records the click, then generates and records the ID for that session (in most cases the transaction ID).
4. TUNE immediately directs the user to the offer’s landing page, including ID for that session in the offer URL.
5. User sees offer’s page on advertiser’s site. Advertiser’s site handles recording that session’s ID however it deems fit, such as storing it as a variable in an e-commerce site or SDK in a mobile app.

When the user converts on that offer:

1. The advertiser’s server sends a signal to TUNE (a.k.a. fires a postback) that includes the ID TUNE initially supplied. The user is not directed back to TUNE in any way.
2. TUNE records the conversion for that session.

TUNE has another great support article explaining postback tracking.

Use postback tracking when:

You have the technical resources available to implement the server-side calls (see below for details on implementation).

Pros and Cons of Pixel Tracking

Pros:

• Pixel tracking is extremely easy to implement. Because it’s just copying and pasting code into the HTML of your website, you don’t need to be a developer to set up tracking. Along the same lines, the learning curve for implementation is not as steep.

Cons:

• Pixel tracking doesn’t work if the conversion occurs on a mobile device. That means conversions on mobile web, in the app stores, and in apps will not register. (Mobile devices and smartphones usually have cookies blocked as a default setting, so a cookie will never be placed on mobile in the first place.)
• Pixel tracking is much more prone to fraud. As you can imagine, because the tracking is done in the browser, it would be fairly easy for a tech-savvy affiliate to fire pixels without an actual conversion occurring.  
• Sometimes, pixels just don’t fire and you won’t know why. A possible reason for this could be that the user cleared their cache between click and conversion, but occasionally the reason is unknown. Reporting will be of little help for troubleshooting, because you won’t have server logs to utilize.
• For all of these reasons (and others), pixel tracking is highly inaccurate.

Pros and Cons of Postback Tracking

Pros:

• Much more reliable because all tracking is done server-side, so you’re leaving a lot less up to chance.
• Much easier to troubleshoot, using TUNE’s server logs.
• Less prone to fraud, and many more options available to mitigate fraud, like adding an offer whitelist, advertiser security token, or hashing the postback URL. Read more about preventing postback fraud.
• You have the option to set up a global postback (on a per advertiser basis), where a single postback implementation can register a conversion for all offers for that advertiser. Pixels don’t have that option.
• In general, postback tracking will allow more options for conversion firing beyond when the user is on the webpage. Instead of being limited to a simple page load, you can have your advertiser send back the conversion URL whenever they please. This will become helpful if your advertiser doesn’t want to register conversions until after an order has shipped, or a lead has been qualified, for example.
• Postback tracking works on mobile devices! Remember, pixel tracking will not work on a smartphone or mobile device.

Cons:

• Postback tracking is harder to implement. It requires direct communication between the network and the advertiser to make sure that the ID is passed into the correct parameter, and then it requires technical implementation on behalf of the advertiser to store and pass back the value. The advertiser will need to have someone with server-side HTTP experience in order to code the requests.
• Implementation time varies widely. Postback tracking could be set up in a matter of minutes, but for some advertisers, it could take an entire day to code the database to store the IDs.

Want more information? Check out our blog series on digital tracking methods, or download the full e-book: How to Become a Track Star: Your Guide to Tracking for Performance Marketing Campaigns.

Author

Becky is the Senior Content Marketing Manager at TUNE. Before TUNE, she handled content strategy and marketing communications at several tech startups in the Bay Area. Becky received her bachelor's degree in English from Wake Forest University. After a decade in San Francisco and Seattle, she has returned home to Charleston, SC, where you can find her strolling through Hampton Park with her pup and enjoying the simple things between adventures with friends and family.