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Android 7.0 or newer. Play keeps you updated automatically; the APK is there if you would rather not use Play, and is the same build. Desktop builds are unsigned for now, so your system may warn on first run.
Every release publishes SHA256SUMS.txt alongside the files.
Checking takes one command and proves the file you have is the file that was
built:
sha256sum -c SHA256SUMS.txt --ignore-missing
On macOS use shasum -a 256; on Windows,
Get-FileHash in PowerShell.
Z is on Google Play as Z Messenger. The Play build and the APK above come from the same tagged release and the same CI pipeline, so you can check either against the published checksums.
Google Play and the Google Play logo are trademarks of Google LLC.
The source is published and the protocol is fully specified, so you can build from the repository rather than trusting a binary at all. Personal self-hosting of the relay is expressly permitted; see self-hosting.