diff --git a/Data-format.md b/Data-format.md
index 3433066..79de064 100644
--- a/Data-format.md
+++ b/Data-format.md
@@ -55,6 +55,9 @@ Names used in Boostnote is created as a random string by [keygen.js](https://git
 https://github.com/BoostIO/Boostnote/blob/a480ca7b551bf70becf8000047b6608194c5c27c/browser/main/lib/dataApi/createFolder.js#L38:L57
 https://github.com/BoostIO/Boostnote/blob/a480ca7b551bf70becf8000047b6608194c5c27c/browser/main/lib/dataApi/createNote.js#L54:L79
 
+`Image name` is a 10 letters string created by `browser/main/lib/dataApi/copyImage.js` (We'll merge them someday)
+https://github.com/BoostIO/Boostnote/blob/a480ca7b551bf70becf8000047b6608194c5c27c/browser/main/lib/dataApi/copyImage.js#L20
+
 # Note hash
 Each note has a unique hash for jumping a note to a note. You can check it in InfoPanel.
 ![image](https://user-images.githubusercontent.com/11307908/31156181-c3b37e08-a8ed-11e7-95f8-c0206aef839c.png)