Skype for Business Server (S4B) replacement.
Topsecret is a secure, end-to-end encrypted alternative for Skype for Business Server (S4B).
- Secure 1:1 and group VoIP
- Complete collaboration platform
- End-to-end encrypted
- On-premise or in the cloud

More than a Skype replacement.
Topsecret replaces Skype for Business VoIP capabilities, and offers the transformative power of a modern - and unique - collaboration platform.
Empower your users with easy voice and video calls, secure connectivity, lively chat rooms, persistent messaging, productivity boosting in-room widgets, data feeds and integrations.
- 1:1 and group voice and video
- 1:1 and group messaging
- Powerful admin functions and permissions
- Voice messages, read receipts and reactions
- Editable messages
- File and screen sharing
Flexible deployment for
security-conscious organisations.
Topsecret can be deployed on-premise, as a fully managed hosted service or a combination of both.
Multiple homeservers can give individual departments their own system - and data sovereignty - with private federation providing secure connectivity across an entire organisation.
Topsecret also supports air-gapped, low-bandwidth and peer-to-peer environments.
Delight your users.
Delight your users with an intuitive messenger-style interface, on desktop and mobile. Single click 1:1 and group voice or video calls, flexible room creation and chat settings, in-room widgets, data feeds and integrations.

- Spaces to organise people and discussions
- In-room widgets; from calculators and calendars to Spotify
- Integrations to share and analyse data in real time
- Emojis, polls, stickers and reactions to stimulate discussion and decision-making
More secure than Skype for Business.
End-to-end encryption
Topsecret is end-to-end encrypted; even if a server or network is compromised, encrypted data can’t be viewed.
Message security
Messages are decrypted per-device, rather than per-user, to add an extra layer of security.
Cross-signed device verification
Cross-signed device verification guards against man-in-the-middle style attacks.
Fast and simple migration.
Skype for Business Server is approaching End of Life, and it has no on-premise migration path.
Topsecret is the natural replacement. It offers the same data ownership model, but with the added protection of end-to-end encryption and a complete enterprise messaging and collaboration platform.
Topsecret is helping all types of organisations migrate from Skype for Business.
Our Skype bridging service, in particular, helps large organisations migrate per department or by region. It enables Topsecret and Skype for Business users to message each other, with a native look and feel, without switching apps.
And of course, being Matrix-based, Topsecret also bridges to traditional collaboration and messaging apps such as Microsoft Teams, Slack, WhatsApp and Signal.
Skype
MS Teams
Cisco Webex
Rocket.chat
Mattermost
Wire
Topsecret
Viable product roadmap
On-premise
Innovation
End-to-end encryption
Cross-signed device verification
Open standard
Open network
No vendor lock-in
Microsoft Teams is not a secure replacement for Skype for Business Server
The University of Innsbruck chose Topsecret over Microsoft Teams to be its university-wide real time collaboration platform for 5,000 employees and 27,000 students; all hosted on-premise.
Read the case study
Enterprise functionality.
An end-to-end encrypted environment, with enterprise functionality. Support for E2EE search, antivirus and data loss prevention.
Delegated authentication (including LDAP for Active Directory) and group sync enable easy provisioning/deprovisioning, Single Sign-On and secure access management.
Built on Matrix
Matrix is an open network for secure, decentralised communication, connecting 80M+ users over 80K+ deployments.
Governed by The Matrix.org Foundation, the Matrix protocol is an open standard with open source implementations, supporting a vibrant developer ecosystem. Topsecret was founded by the team behind Matrix as a way to bring it to the mainstream.