Slack

In 2024, Slack faced significant backlash after users discovered the company's policy of using customer messages and interactions to train its AI/ML models. Critics argued Slack had not adequately informed users about this data usage. The policy required workspace administrators to opt out by contacting Slack directly, rather than providing a simple user-facing toggle, drawing comparisons to other companies' controversial AI training practices.

Slack pledged 1% of company equity, time, and product to community benefit. When Salesforce completed its $27.7B acquisition in 2021, Slack donated $54 million — the balance of the value of its Pledge 1% share reserve — to the Salesforce Foundation. Slack also gave employees seven days of paid volunteer time off and provided free or discounted software to nonprofits.

Slack partnered with the Transgender Law Center to fund creation of a comprehensive ally skills curriculum designed to improve companies' ability to recruit, hire, include, and retain transgender and gender nonconforming employees. The curriculum was made available across the entire tech sector, extending impact beyond Slack's own workforce. Slack also published transparent diversity reports, maintained pay and promotion equity across genders for three consecutive years, and ran programs including Rising Tides sponsorship for diverse high performers.

Slack published detailed diversity reports with EEO-1 filings, conducted third-party salary equity audits, and maintained active ERGs (Earthtones, Abilities, Out). The company partnered with Year Up for workforce training (87.5% intern-to-FT conversion rate), Code2040 for Black and Latinx technologists, and the Transgender Law Center. However, 2020 data showed declining representation: women in management fell from 50.2% to 46.1%, and Black employees represented only 4.5% of workforce.

Slack has published numerous open source projects on GitHub including Nebula (scalable overlay networking tool), PanModal (iOS presentation API), and Kaldb (observability data storage). The company actively contributes to core frameworks including Electron, Webpack, and Vitess. In 2024, Slack open-sourced its CLI tool. Slack also sponsors Kotlin Lang Slack and contributes to projects like Anvil and Insetter.

In 2018, Slack partnered with The Last Mile, FREEAMERICA, and the WK Kellogg Foundation to create Next Chapter, an engineering apprenticeship program helping formerly incarcerated individuals find skilled employment in tech. The program has since expanded to 14 hiring partner companies. Slack was one of the first major tech companies to create a dedicated reentry hiring pathway.

Despite widespread use and privacy advocates calling E2E encryption essential, Slack has never offered end-to-end encryption. In 2018, Slack's CISO stated paying customers were more interested in enterprise key management than E2E encryption. Slack encrypts data in transit and at rest but data remains accessible to Slack's systems and personnel, with workspace owners able to monitor all chats including private ones.

In February 2015, unauthorized individuals gained access to Slack infrastructure including a database storing user profile information: usernames, email addresses, hashed passwords, phone numbers, and Skype IDs. Approximately 500,000 users were affected. In response, Slack added two-factor authentication. In 2019, Slack reset passwords for ~1% of users still using pre-2015 credentials.