Always show file extensions in Finder on Mac

macOS hides filename extensions by default, so a file called Report.pdf shows up simply as Report. That's tidy until you have ten files called "Report" and no idea which is a PDF, which is a Word doc, and which is an old Pages file. One setting fixes this permanently.

Why macOS hides extensions

Apple's reasoning is that most people don't need to think about file types — the right app opens automatically. The downside is that you can't easily see at a glance whether something is a .jpg or a .png, and you can accidentally rename a file and strip the extension entirely, breaking it. For anyone doing real work with files, showing extensions is the right default.

Method 1: Finder Settings (easiest)

In Finder on macOS Ventura, Sonoma, or Sequoia:

1. Open Finder and press ⌘, to open Finder Settings (or choose Finder › Settings from the menu bar).
2. Click the Advanced tab.
3. Tick the checkbox labelled "Show all filename extensions."

Extensions appear immediately — no restart needed. To revert, untick the same checkbox.

Method 2: Terminal command

The setting lives in the global macOS preferences domain, so the Terminal command is slightly different from other Finder settings:

# show file extensions for every file in Finder
defaults write NSGlobalDomain AppleShowAllExtensions -bool true
killall Finder

Finder relaunches and all your filenames now include their extensions. To turn it back off:

# restore the default (hide extensions)
defaults write NSGlobalDomain AppleShowAllExtensions -bool false
killall Finder

Note that this writes to NSGlobalDomain rather than com.apple.finder — it's a system-wide preference, so it applies across all Finder windows and views.

What about individual file extensions?

Even with this setting off, you can always check a single file's extension by pressing ⌘I (Get Info) — the Kind field and Name field both show the full name including extension. But turning on "Show all filename extensions" is far more practical for day-to-day work.

Renaming files safely

Once extensions are visible, be careful when renaming: if you click a filename and edit it, don't delete the extension part. Finder will warn you with a sheet ("Are you sure you want to change the extension?") if you try to change or remove it, so you do get a safety net — but it's easier to just be aware.

Per-file extension exceptions

You can hide the extension for a specific file even when the global setting is on. Select the file, press ⌘I, expand the Name & Extension section, and tick "Hide extension." This per-file override stays put regardless of the global setting — useful for files you always open with a specific app and don't need to identify by type.