Microsoft Blames Slack’s Growth on ‘Inferior Capabilities’ Amid Recent Lawsuit

Key Takeaways

• Slack sues Microsoft in UK over Teams bundling with Office.
• Teams holds ~37% market share vs Slack's 13% as of Nov 2025.
• Microsoft claims Slack's slower growth stems from inferior capabilities, not bundling.
• Salesforce-backed Slack argues bundling limits customer choice and competition.
• UK regulators previously forced Microsoft to offer Teams‑free Office packages.

Pulse Analysis

The lawsuit filed by Slack and its parent Salesforce revives a long‑standing debate over whether software giants can leverage bundled products to dominate adjacent markets. Antitrust authorities in Europe have already nudged Microsoft to separate Teams from its Office suite, offering lower‑priced, Teams‑free options after pressure from regulators. The UK filing suggests that those concessions were insufficient, highlighting the tension between integrated ecosystems and the principle of customer choice in the enterprise software arena.

Market data underscores the competitive imbalance. As of November 2025, Microsoft Teams boasts about 320 million monthly active users and a 37% share of the collaboration‑software market, while Slack trails with roughly 79 million users and 13% market share. Microsoft’s strategy of embedding Teams in Microsoft 365 has accelerated adoption, especially among large, regulated enterprises that prefer a single‑vendor solution for compliance and administration. Slack, backed by Salesforce’s $27.7 billion acquisition, positions itself as a flexible, integration‑friendly platform favored by smaller, agile teams, but its growth has been hampered by the default presence of Teams in the dominant productivity suite.

The outcome of the UK case could have ripple effects across the tech industry. A ruling that deems bundling anticompetitive may compel Microsoft to unbundle Teams globally, potentially opening pricing and feature negotiations for rivals and reshaping enterprise procurement strategies. Moreover, the decision could influence ongoing investigations into Microsoft’s cloud licensing practices, reinforcing a broader regulatory trend toward scrutinizing bundled services that may stifle innovation and limit market entry for challengers. Companies and investors will be watching closely as courts weigh the balance between integrated product value and fair competition.