diff --git a/README.md b/README.md
index 98d3d44be9..8369c8f8f4 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,31 @@ This is the repository for **Lean 4**, which is currently being released as mile
 
 See [Setting Up Lean](https://leanprover.github.io/lean4/doc/setup.html).
 
+## Supported Platforms
+
+### Tier 1
+
+Platforms built & tested by our CI, available as nightly & stable releases via elan (see above)
+
+* x86-64 Linux with glibc 2.27+
+* x86-64 macOS 10.15+
+* x86-64 Windows 10+
+
+### Tier 2
+
+Platforms cross-compiled but not tested by our CI, available as nightly & stable releases
+
+Releases may be silently broken due to the lack of automated testing.
+Issue reports and fixes are welcome.
+
+* aarch64 Linux with glibc 2.27+
+
+### Tier 3
+
+Platforms that are known to work from manual testing, but do not come with CI or official releases
+
+* aarch64 (M1) macOS - may also [use x86-64 releases via Rosetta](https://github.com/leanprover/elan#manual-installation)
+
 # Contributing
 
 Please read our [Contribution Guidelines](CONTRIBUTING.md) first.