Messenger Interoperability: Well-Intended, but Bad for Data Privacy

WhatsApp has been open to third-party messaging services since fall 2025. Under the EU’s Digital Markets Act (DMA), the platform is required to support interoperability with alternative chat services. While we support the DMA’s underlying goals, we have decided not to implement interoperability with WhatsApp for several reasons.

The EU’s Digital Markets Act (DMA) requires so-called “gatekeepers” – large technology companies such as Apple, Google, and Meta – to open their services to third-party providers. The aim is to reduce the market power of dominant platforms, promote fair competition, and give consumers greater freedom to choose the services they use.

As part of these requirements, WhatsApp updated its technical specifications in fall 2025, making it possible, in principle, for messages to be exchanged between WhatsApp and other messaging services.

Threema does not support interoperability with WhatsApp. There are several reasons for this:

1. Privacy and security would be compromised

Interoperability cannot be implemented without jeopardizing our users’ privacy, as most apps differ fundamentally in how they implement key concepts and security mechanisms. One example is user identification: Threema uses anonymous IDs, whereas WhatsApp relies on phone numbers.

Interoperability would require compromises that effectively reduce privacy protection to the lowest common denominator. This would affect areas such as data protection and metadata minimization.

In addition, once data is transferred to WhatsApp, we have no way of verifying exactly how it is processed or handled, particularly because WhatsApp is not open source.

2. It could cement the monopoly

Although the DMA aims to foster competition, we do not believe interoperability with WhatsApp would necessarily lead to greater diversity in the messaging landscape. In fact, even the opposite could happen: if people can communicate with their Threema contacts directly from WhatsApp, they have less reason to download and actively use Threema (or any alternative chat app).

3. Our business model would be undermined

If fewer people download the Threema app as a result, the source of revenue disappears. This is particularly significant for a traditional business model like ours. Threema is not funded through advertising, donations, or the monetization of user data. Instead, our development is financed through app sales.

To continue developing Threema – and to build and maintain a potential interoperability interface with WhatsApp – we depend on revenue from app purchases.

For these reasons, we have decided not to implement interoperability with WhatsApp. Privacy and security are the foundations of Threema. We are not willing to compromise on either.