Change file extensions on Mac without the warning

When changing extensions is part of your routine — retagging a batch of .jpeg files as .jpg, fixing a folder of mislabelled downloads — Finder's "Are you sure?" fires on every single file and turns a two-minute job into a click marathon. Switch the confirmation off once, then rename in bulk from Finder or the Terminal without interruption.

Switch off the confirmation

Do this first so nothing interrupts the renames that follow. Either route works:

1. Open Finder → Settings (Cmd+,) and click Advanced.
2. Uncheck Show warning before changing an extension.

Or set it from the shell and be done:

# disable the extension-change warning
defaults write com.apple.finder FXEnableExtensionChangeWarning -bool false
killall Finder

# undo: re-enable it
defaults write com.apple.finder FXEnableExtensionChangeWarning -bool true
killall Finder

The preference behaves the same across macOS Ventura, Sonoma, and Sequoia. With it off, every rename below goes through in silence.

Rename a batch in Finder

Finder has a built-in multi-file rename that most people never find:

1. Select all the files whose extension you want to change.
2. Right-click the selection and choose Rename….
3. Pick Replace Text, put the old suffix (e.g. .jpeg) in Find and the new one (.jpg) in Replace with, and click Rename.

All selected files change at once, no dialogs. Because "Replace Text" is a plain find-and-replace, keep the leading dot in both fields so you only touch the extension, not matching text in the middle of a name.

Or do it in the Terminal

For real volume, the shell is faster. To turn every .jpeg in a folder into .jpg:

# rename all .jpeg files to .jpg in the current folder
for f in *.jpeg; do mv "$f" "${f%.jpeg}.jpg"; done

The Finder warning never applies here — it only guards renames made in Finder itself — so this works whether or not you flipped the setting. That said, disabling the dialog keeps Finder and Terminal behaving consistently, which is one less surprise when you switch between them.

One caution for batch renames

Changing an extension never converts the file — song.wav renamed to song.mp3 is still a WAV that some apps will reject. For a batch that needs real conversion, use a converter and keep the rename for genuinely mislabelled files. And if you want the whole suffix visible while you work, turn on Show all filename extensions first.