diff --git a/LogarithmPlotter-file-format-v1.0.md b/LogarithmPlotter-file-format-v1.0.md
index 8db2ed1..aa239fe 100644
--- a/LogarithmPlotter-file-format-v1.0.md
+++ b/LogarithmPlotter-file-format-v1.0.md
@@ -1,5 +1,5 @@
 # LogarithmPlotter file format v1.0
-LogarithmPlotter files (with the extension .lpf, .lgg, .json), are json-encoded files.
+LogarithmPlotter files (with the extension .lpf), are json-encoded files with a 5 byte header `LPFv1`.
 
 JSON Tree: