Mattermost vs Slack: Privacy Comparison
In this comprehensive privacy comparison, we analyze Mattermost and Slack across six critical dimensions: data collection practices, encryption implementation, third-party data sharing, user privacy controls, transparency, and historical track record. Both services serve similar needs, but their approaches to user privacy differ significantly. Our analysis reveals that Mattermost offers a meaningfully better privacy experience overall, though each service has relative strengths and weaknesses worth understanding in detail.
What the Numbers Say
Here is the result of weighing both services across the dimensions that decide real-world privacy. Across the six privacy dimensions we score, Mattermost finishes ahead of Slack, 48/60 to 36/60. That total reflects a privacy face-off in which one service is consistently the more privacy-respecting choice, even though both cover the same functional ground.
Most of the distance between these services opens up on Data Collection: Mattermost 8/10 versus Slack 6/10. Data Collection is where they come closest, a mere 2-point gap (8 vs 6 out of 10). Keep reading to see exactly how the gap was earned, category by category.
How Each Service Collects Data
Every privacy assessment starts with data collection. How much a service gathers, stores, and processes about its users is what ultimately drives the privacy risk of using it. Mattermost takes a leaner approach here, capturing only the data strictly required to make the service work. Its rival pulls in a wider net of information -- behavioral patterns, device identifiers, and usage analytics that go well past what the core features actually need. Our marks were Mattermost 8/10 and Slack 6/10 in this area. What separates them is not merely how much is gathered but why it is gathered and whether it is truly needed.
How Strong Is the Encryption
Encryption guards user data as it moves and while it sits at rest, and how well it is built differs enormously from one service to the next. Mattermost puts tougher encryption in place, with sturdier protocols shielding data in transit and stronger safeguards for what is stored. The two implementations part ways on coverage (which data actually gets encrypted), on strength (which algorithms and key lengths back it up), and on whether end-to-end encryption is in play (which keeps even the provider from reading user content). For encryption, Mattermost scored 9/10 while Slack scored 7/10.
Sharing Data With Outside Parties
How services share data with third parties is a critical privacy dimension. This includes sharing with advertising networks, analytics providers, business partners, and in response to government requests. Mattermost maintains more restrictive policies regarding third-party data access. The data sharing practices affect not just privacy but also the security of user information, as each additional party with access represents a potential breach vector. Scores: Mattermost 10/10, Slack 8/10.
Controls You Can Actually Use
The availability and effectiveness of user-facing privacy controls determine how much agency individuals have over their own data. This includes settings for data collection opt-out, download and deletion capabilities, granular permission controls, and the ease with which users can exercise their rights under applicable privacy regulations. Mattermost provides more comprehensive and accessible privacy controls. Scores: Mattermost 6/10, Slack 4/10.
Openness About Data Practices
At its core, transparency is about how clearly a service tells users what happens to their data. That means how understandable the privacy policy is, whether transparency reports exist, how promptly privacy inquiries are addressed, and whether changes to policy are flagged proactively. Mattermost is the stronger performer on transparency overall. Without clear and accessible privacy communication, informed consent and trust are impossible. Scores: Mattermost 7/10, Slack 5/10.
Historical Track Record
A service's history of privacy incidents, regulatory actions, and responses to vulnerabilities provides important context. Mattermost has a stronger historical record on privacy, with fewer incidents and more responsible handling of the issues that have arisen. Past behavior is often the best predictor of future privacy practices. Scores: Mattermost 8/10, Slack 6/10.
The Final Verdict
Adding everything up, our full analysis lands Mattermost at 48/60 and Slack at 36/60. For privacy, the overall winner is Mattermost. The two cover much the same functional ground, but the winner takes a more privacy-respecting stance across the dimensions that count for the most. Even so, no service is flawless, and whichever option you pick, you should always tune its privacy settings deliberately. We suggest pairing your choice with extra privacy tools, a VPN, DNS-level ad blocker, and privacy-focused browser, so you end up with a well-rounded privacy posture. And if your threat model demands the very highest level of privacy, it is worth asking whether an even more privacy-focused alternative exists in this category beyond the two compared here.