diff --git a/README.md b/README.md
index 6e56a1b..7624dbd 100644
--- a/README.md
+++ b/README.md
@@ -9,8 +9,14 @@ produced by Fediverse bots (think an interactive game where the game board
 is rendered to an image or a text file on demand). There are sure to be many 
 other uses I didn't think of.
 
+The server internally uses hash-based de-duplication with reference counting.
+If the same file is uploaded more than once, only one copy is stored in memory
+(and on disk).
+
 The uploaded files have a lifetime of 10 minutes, which can be shortened or 
-extended up to 1 hour (or more, as configured).
+extended up to 1 hour (or more, as configured). If file-backed persistence
+is enabled (off by default), all uploaded (non-expired) files will survive 
+server restart.
 
 ## Config file