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How Postback URLs Track Your Conversions When Pixels & Cookies Fail

November 23, 2022  ·  5 min read
Kseniia Kyslova
Kseniia Kyslova, Senior Marketing Copywriter at Epom

Third-party cookies are on their way out, so we're looking for an alternative to pixel tracking. One of the most viable methods is server-to-server tracking. It would provide accurate metrics even in a cookieless world.

Do you still use pixels for tracking the performance of your ad campaigns? Bad news. You might be overseeing up to 20% of conversions due to technical flaws in browsers. And this number worsens as sites introduce stricter data privacy regulations and site visitors opt out of cookies.

However, there's some good news. You can track conversions with a method that isn’t affected by any of that. It’s server-to-server tracking. There is only one downside to it: implementation complexity. But if you're committed to learning it anyway and seeing its benefits, keep reading.


What Is Server-to-Server Tracking?

S2S tracking allows you to attribute conversions to the ads that brought users to your website or app. Conversion data is exchanged between servers on the backend of apps, sites, analytics platforms, and DSPs, with the help of postback URLs.

Why S2S Takes the Edge Over Pixels

Pixel-based tracking relies on users' browsers and devices. S2S tracking does not. This is why server-based tracking is not affected by technical flaws or privacy settings on the user's end. No ad discrepancy issues would be caused by it.

Let’s look at some scenarios when a conversion wouldn’t be captured if tracked by the pixel but would be captured if tracked server-side:

  • A site visitor uses the Safari or Firefox browser. By default, the browser blocks the third-party cookies your pixel tracking relies on.
  • A site page doesn't load correctly on the user's device, and some flaws with the JS code occur. The pixel code doesn't execute correctly and doesn’t capture a conversion.
  • Pixel code fires one time, but that very moment your conversion tracking platform’s server is busy, and it doesn’t pick up the data.
  • You want to track conversions on a site, but the site owner refuses to add your pixel tracker because it may slow down their site load speed.
  • A person makes a conversion action in a mobile app on their iPhone, but iOS doesn’t support pixel conversion tracking for user privacy concerns.

Media buyers discuss pixel tracking accuracy in professional communities and share that pixel tracking can underreport up to 20% of conversions for the mentioned pitfalls.

None of the described scenarios would affect S2S tracking. The conversion measurement will remain excellent even after Google Chrome finally phases out third-party cookies.

How Server-Side Tracking Works

In server-to-server tracking, all conversion data is collected, stored, and exchanged on the backend of apps and websites. Backend servers run special scripts to collect data. Then, they exchange data using postback URLs.

What Is a Postback URL?

A postback URL is a link generated by software that needs to receive information about conversions on sites or in apps. It can be a programmatic advertising platform, an ad server, a data management platform, an analytics tool, or other parts of the advertising ecosystem.

Every tool generates its own postback URL. The link contains macros or placeholders for data points the tool needs to receive. A server on the backend of a site gets postback URLs from the tool and checks for macros. Afterward, it swaps the macros for actual conversion data and sends the link back.

Postback URL tracking process

Contextual Data In Postback URLs

The list of available macros can be long and vary by platform. You should use different macros depending on the data you want to receive. In Epom DSP, for example, you can select from over 50 macros to get information about user devices, ad placements, bid prices, etc.

You can use $!{source} macro to indicate SSP, $!{bid} macro to capture the bid price, $!{app} or $!{site} macros to indicate where the conversion came from, and many more. Here is an example of the postback URL you can generate in Epom DSP:$!{tid}&app=$!{app}&event=0&event=1&price=1.23

Most macros are optional. However, there is a mandatory macro to include in the link to score conversions in Epom DSP. This is the $!{tid} macro. It captures the unique transaction ID for every user session. This ID is used to attribute conversions to specific ads.

Setting up Postback URL Tracking

Let’s say you run programmatic ads with Epom DSP and use conversion tracking software to orchestrate data collected from your site or app. To optimize your ad campaigns, you want these tools to communicate server to server. So, you’ll have:

  • A sending server on the backend of your tracking tool
  • A receiving server on the backend of your Epom DSP

Two options exist depending on the amount of conversion-related data you want to exchange:

  1. Simple tracking. Only the standard transaction ID macro should be included in your postback URL. You just need to get the template postback URL from Epom DSP and paste it into your conversion tracker. The interfaces of both platforms have dedicated tabs for this.
  2. Advanced tracking. To get detailed information about conversions, your postback URL should contain a lot of macros. In this case, you’ll need assistance from technical support teams. They’ll help you integrate the platforms and map the macros used by Epom DSP to those used by the conversion tracker.

By connecting two platforms, you can implement media buying optimization. You'll see conversion data in the Epom DSP analytics dashboard. Additionally, you can use this data in Epom DSP Bidding Autopilot to optimize your campaign’s CPA automatically.

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Benefits of Server-to-Server Tracking Wrapped Up

You'll get the most accurate and complete data on conversions from your ads once you set up server-to-server tracking. This tracking method is reliable for several reasons:

  1. Conversion events. You can track up to three conversion events with one postback URL. It'll help you better understand your buyers. A conversion can be an app download, finishing an onboarding tutorial, or an in-app purchase.
  2. Fault resilience. Conversion data is stored on servers, not in users' browsers, which ensures it won't be lost. Additionally, the sending server calls the receiving server multiple times until it picks up the conversion, preventing data loss due to server overload or downtime.
  3. No fraud. Since every conversion has a unique transaction ID, the server-to-server method is fraud-prone. One conversion won’t be counted twice.
  4. Data safety. You can encrypt any sensitive data you collect and exchange server-side.
  5. Compliance. No matter what their data privacy policies are, all OS and devices support postback URL tracking. Conversions can be tracked on nearly any website and app, but the scope of available data varies.

Only server-to-server tracking can measure conversions with an accuracy approaching 100%. It's especially useful for media buyers who deal with affiliate offers and in-app ads.

Even if you don't fall into either of these categories, now is the time to get your head around it. A cookieless future is coming. At some point, you'll have to switch from cookie-based tracking to its alternative anyway.

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