macOS 10.13 High Sierra was a great operating system. It brought APFS (Apple File System) to the world. But in the SaaS era, software is a perishable good. Slack didn't just "drop support" out of spite; the code literally cannot breathe the air of a system that is half a decade out of date.
Apple stopped issuing security patches for High Sierra in . If you are running 10.13, your machine has known unpatched vulnerabilities, including the infamous CVE-2019-8518 (a logic issue allowing malicious applications to bypass Gatekeeper). slack mac 10.13
By refusing to run on High Sierra, Slack protects itself from liability. If a hacker used an unpatched macOS kernel bug to inject code into Slack’s memory, users would blame Slack, not Apple. Modern apps refuse to run on EOL (End of Life) systems to maintain their security reputation. For the user, the experience is abrupt. You open Slack. You see the splash screen. Then you see: Can't open Slack You have macOS 10.13. Slack requires macOS 10.14 or later. If you have an old version of Slack cached, you might get the "Update Required" yellow banner. However, the API servers eventually reject the old client, returning an http_platform_failure error. You can read messages, but you cannot send them, join huddles, or upload files. Workarounds (And Why They Fail) For users clinging to a 2012 MacBook Pro that cannot officially upgrade to Ventura, what are the options? macOS 10
Tools like dosdude1 's macOS Mojave/Catalina patchers allow unsupported Macs to run newer OSes. However, this kills graphics acceleration. Slack, ironically, becomes a stuttering mess on patched hardware. Slack didn't just "drop support" out of spite;