Open source projects like Mattermost and Rocket.chat aim to beat Slack with features it doesn't yet have
Klint Finley / Wired :
Context & Ripple Effects
In March 2016, Slack owns the team-chat conversation but not the whole market: Mattermost and Rocket.chat are pitching open-source, self-hostable alternatives whose selling point is capability plus control rather than network effects. The relationships data shows Mattermost backing that pitch with capital — a $20M Series A led by Redpoint, then a $50M Series B led by Y Combinator Continuity, roughly $70M total — which turns a hobbyist alternative into a funded challenger.
The arc that follows validates why this mattered: within months Slack was running a defensive New York Times ad that read as fear of Microsoft (an ad widely read as undermining its own message), and by 2020 CEO Stewart Butterfield was doing damage-control interviews about competing with Microsoft directly (his Q&A on the Teams rivalry). Open source was the first crack in the assumption that chat was a winner-take-all market.
First-order effects
- Buyers who need self-hosting or data control — regulated industries and security-conscious enterprises — get a funded, credible option instead of choosing between adopting Slack or building internally.
- Slack faces feature-based competition for the first time at scale: Mattermost and Rocket.chat can ship capabilities Slack hasn't prioritized without waiting on Slack's roadmap.
Second-order effects
- Microsoft answers with distribution rather than features, folding Teams into its cloud-OS strategy while Slack counters with Connect and an enterprise-social-network framing (the Stratechery breakdown of the two visions) — leaving the open-source players owning the self-hosted niche both incumbents ignore.
- Front's asynchronous-inbox tooling shows adjacent startups positioning against Slack's synchronous model entirely (Mathilde Collin's case for async), fragmenting 'team communication' into segments no single vendor covers.
Third-order effects
- If the pattern holds, team chat stops being a product category and becomes a platform war — a shift researchers later formalized when they argued Slack and Teams need OS-style app vetting because their third-party ecosystems became the real attack surface (the app-model critique).
- Open-source challengers structurally cap incumbents' pricing power: as long as a funded Mattermost exists, Slack cannot treat enterprise accounts as captive, pushing differentiation toward ecosystem lock-in rather than per-seat fees.
The trend: Team messaging is shifting from a feature race among chat apps to a platform-and-control contest, where open-source alternatives set the floor on price and lock-in for proprietary incumbents.