diff --git a/README.md b/README.md
index a508412f7fc7edc5273863c1eb2e847ee42af93f..4cfd91b3716ecbd8c625e4b13d9e1ea550a0e52d 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,13 @@ catch {
 }
 ```
 
+## Custom File Extensions
+
+Before unzipping files, the source path is checked to make sure the file type is valid (e.g. the file is a .zip). If the file is not valid then we throw an error, however we understand that there might be some file types you wish to accept, even though it might not exist by default in the supported extensions list. As a result you can add custom file extensions to the list of accepted extensions.
+```
+Zip.addCustomFileExtension("file-extension-here")
+```
+
 
 ### Setting up with Carthage