You can hide your filename extensions - which leaves renaming error free.
If you have the extension showing in the filename it will be removed when you type in a new name, unless you type the extension as <filename.jpg> for example.
Step 1: Open a new Finder window on your Mac.
Step 2: In the Menu bar, go to Finder > Preferences.
Step 3: Click on the Advanced tab.
Step 4: Select the box that says “Show all filename extensions”. If you want to hide file extensions, just uncheck the box.
It’s as simple and quick as that. If like me you like to show filename extensions, then follow these easy steps.