The Caller SDK – Give your app the engagement it deserves!

All app developers face the same two challenges. The first is persuading people to download their app. The second is persuading those people to actually use it.

The latter is the engagement problem. And Calldorado’s Caller SDK solves it to an astonishing degree. It does this in a unique way: by linking the app to a person’s call activity. More precisely, the Caller SDK brings the app to the user’s home screen every time they make, receive or miss a call.

This simple technique ensures that the app remains ‘front of mind’ all the time.

Since users typically make/receive/miss around five calls a day, that’s five chances for a developer to remind customers about their app.

As a result, user engagement soars.

In fact, apps that use the Caller SDK have found that the number of ‘app opens’ triggered by a call can be up to 40x higher than ‘organic’ opens triggered by users themselves.

To illustrate the impact of the Caller SDK, let’s do a walk-through of user experience with a real-life example: a note-taking app called Notes.

  1. The developer codes in the Caller SDK. This is a very simple and quick task, for which there is a handy guide that takes you through every step in detail.
  2. The SDK adds a feature that integrates the app’s functions directly into the phone’s caller display.
  3. The developer customizes this feature to align with the Notes user interface.
  4. A user downloads the app and gives permission for the app to use their caller display.
  5. The user receives a call. After finishing the call, they decide to make a note in the Notes app. The app is already presented on the screen alongside relevant call information. Therefore the user can just type directly in the call information screen without having to manually open the app separately.


As the above example shows, some app categories are especially well-suited to Caller SDK. These include any whose core function relate to calls, messaging, and communication such as:

  • Email
  • Note-taking
  • Messaging
  • Launching
  • Notifications
  • Calendar
  • Video calling
  • …and more.


Dozens of apps from these categories around the world currently use the Caller SDK. They have all experienced a significant uplift in user engagement. And since extra engagement boosts ad views, they have boosted their income too.

Indeed, some Caller SDK-enabled apps have doubled their revenue in three months.

The Caller SDK is free of charge and takes a minimum amount of time and effort to integrate.

It operates on a revenue share model, so there is little or no risk to developers. The model ensures that Calldorado only gets paid when its developers succeed.



For any developer considering a new app engagement service, only two metrics really matter.

  1.  The number of organic ‘user triggered’ opens.
  2. The number of opens triggered by the service under consideration.


The bigger the gap, the more compelling the app engagement service.

To test the SDK’s impact on ‘opens’, Calldorado studied the performance of three apps that use Caller SDK to improve user engagement. The results were as follows:

Product: All Email Access (USA).
Improvement: 33x more app opens with Caller SDK.

Product: Voice Recorder (USA).
Improvement: 23x more app opens with Caller SDK.

Product: Notes (South Korea).
Improvement: 40x more app opens with Caller SDK.

While improving engagement is very welcome, the key benefit of the Caller SDK is the effect this has on revenues.

Here’s a real-life example. Zoran Gasic’s callX Automatic Call Recorder app achieved more than 10 million installs. But its income was modest.

This changed completely after Gasic’s company, SMSROBOT, added the Caller SDK.

“All KPIs skyrocketed after just a couple of days,” says Gasic. “We doubled our revenue in just three months. User retention remained completely stable and the number of sessions per user increased 10x.”


To find out if the Caller SDK is a fit for your app, contact Calldorado today.

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