diff --git a/blake2b/blake2b.go b/blake2b/blake2b.go
index c160e1a4e3..d2e98d4295 100644
--- a/blake2b/blake2b.go
+++ b/blake2b/blake2b.go
@@ -5,6 +5,8 @@
 // Package blake2b implements the BLAKE2b hash algorithm defined by RFC 7693
 // and the extendable output function (XOF) BLAKE2Xb.
 //
+// BLAKE2b is optimized for 64-bit platforms—including NEON-enabled ARMs—and
+// produces digests of any size between 1 and 64 bytes.
 // For a detailed specification of BLAKE2b see https://blake2.net/blake2.pdf
 // and for BLAKE2Xb see https://blake2.net/blake2x.pdf
 //
diff --git a/blake2s/blake2s.go b/blake2s/blake2s.go
index 5fb4a9ecd1..e3f46aab3a 100644
--- a/blake2s/blake2s.go
+++ b/blake2s/blake2s.go
@@ -5,6 +5,8 @@
 // Package blake2s implements the BLAKE2s hash algorithm defined by RFC 7693
 // and the extendable output function (XOF) BLAKE2Xs.
 //
+// BLAKE2s is optimized for 8- to 32-bit platforms and produces digests of any
+// size between 1 and 32 bytes.
 // For a detailed specification of BLAKE2s see https://blake2.net/blake2.pdf
 // and for BLAKE2Xs see https://blake2.net/blake2x.pdf
 //