Illustration for How to Show and Change File Extensions on a Mac

How to Show and Change File Extensions on a Mac

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Illustration for How to Show and Change File Extensions on a Mac

Quick Answer

To show file extensions for all files on your Mac, open Finder, choose Finder > Settings, select Advanced, and turn on Show all filename extensions.

To show or hide the extension for one file:

  1. Select the file in Finder.
  2. Choose File > Get Info.
  3. Expand Name & Extension.
  4. Select or clear Hide extension.

To change an extension, rename the part after the final period in the filename. macOS may display a warning asking whether you want to keep the new extension. Choose Use .[new extension] only when you know the file is genuinely compatible with that format.

What Is a File Extension?

A file extension is the group of letters after the final period in a filename. It tells macOS and your apps what type of file it is and which app should normally open it.

Examples include:

  • Report.docx — a Microsoft Word document
  • Photo.jpg — a JPEG image
  • Song.mp3 — an audio file
  • Archive.zip — a compressed archive
  • Spreadsheet.xlsx — an Excel workbook

macOS can hide extensions in Finder to make filenames look simpler. The extension still exists; it is merely not displayed. Showing extensions makes it easier to identify file types, rename files accurately, and spot potentially misleading filenames.

Changing an extension does not convert the file to a different format. For example, renaming Photo.jpg to Photo.png does not turn a JPEG image into a PNG image. It only changes the label at the end of the filename. To convert a file, open it in an appropriate app and use that app’s export or save options.

Show File Extensions for All Files

The simplest way to show the Finder filename extension for every file is to change Finder’s settings.

  1. Open Finder.
  2. In the menu bar, choose Finder > Settings.
  3. Select Advanced.
  4. Turn on Show all filename extensions.
  5. Close the Finder Settings window.

Finder should now display extensions for files throughout your folders.

For example, a file that previously appeared as Vacation Photo may now appear as Vacation Photo.jpg.

What This Setting Changes

This setting changes how Finder displays filenames. It does not rename files or convert them. It also does not change which app opens a file.

When all extensions are visible, you can more easily:

  • Distinguish between similar files with different formats
  • See whether a downloaded file is an image, document, archive, or application
  • Rename an extension deliberately
  • Identify filenames with multiple extensions, such as document.pdf.exe

The setting applies broadly in Finder, but individual files can still have their own Hide extension setting.

Show or Hide the Extension for One File

You can control the extension display for an individual file without changing Finder’s setting for every file.

  1. Open Finder and locate the file.
  2. Select the file.
  3. Choose File > Get Info, or press Command-I.
  4. In the Info window, click the disclosure arrow next to Name & Extension if that section is collapsed.
  5. Select Hide extension to hide the extension, or clear it to show the extension.
  6. Close the Info window.

If Show all filename extensions is enabled in Finder, clearing Hide extension ensures that the selected file’s extension remains visible. Selecting Hide extension hides that file’s extension even when Finder is showing extensions generally.

Show an Extension Temporarily

If you normally hide extensions but want to inspect one file, Get Info is useful. You can view the complete filename in the Name & Extension section without changing Finder’s global setting.

You can also select a file and press Command-I, then review its Kind, Name & Extension, and Open with information.

Change a File Extension Safely

You can change a filename extension directly in Finder. Do this only when the file’s contents already match the new format or when you understand the consequences.

Warning: Renaming an extension can make a file difficult to open. It does not convert the file. Before changing it, make a copy of the file or confirm that you can restore the original extension.

Method 1: Rename the File in Finder

  1. Open Finder and locate the file.
  2. Select the file.
  3. Press Return, or choose File > Rename.
  4. Edit the part of the filename after the final period.
  5. Press Return to save the new name.
  6. If macOS displays a warning, review it carefully.
  7. Choose Use .[new extension] to keep the new extension, or choose Keep .[old extension] to cancel the extension change.

For example, you might rename:

notes.txt

to:

notes.rtf

However, this does not convert a plain-text file into a Rich Text Format document. The file must already contain data in a format that the app can interpret as RTF.

Method 2: Use Get Info

The Get Info window can be useful when the extension is hidden or when you want to review the file before renaming it.

  1. Select the file in Finder.
  2. Choose File > Get Info.
  3. Expand Name & Extension.
  4. Click in the filename field.
  5. Edit the extension after the final period.
  6. Press Return.
  7. Confirm the warning by choosing Use .[new extension] or cancel by choosing Keep .[old extension].

This method also lets you check whether Hide extension is enabled before you make a change.

Understand the Extension Warning

When you change a file extension, macOS may warn that changing the extension could make the file open in the wrong app. The dialog gives you a choice:

  • Use .[new extension] — accepts the new extension
  • Keep .[old extension] — leaves the original extension in place

Choose Use .[new extension] only if you intended to change the extension. Choose Keep .[old extension] if you are unsure or changed the wrong part of the filename.

If you accidentally accept the wrong extension, rename the file again and restore the original extension. A file may still contain its original data, even if its extension is incorrect.

Do Not Confuse Renaming With Converting

Changing a file extension is different from converting a file.

Renaming an Extension

Renaming changes only the filename. For example:

image.jpg → image.png

The file’s internal data remains JPEG data. An image editor may still recognize it as a JPEG, while other apps may refuse to open it because the extension says PNG.

Converting a File

Converting creates a file with data encoded in another format. The correct process depends on the file type and the app you use.

Examples:

  • Open an image in an image editor and use File > Export or File > Save As
  • Open a document in a compatible editor and use its export or save options
  • Open an audio file in an audio app and choose an available conversion or export command

If you need a true format conversion, use the application’s conversion tools rather than simply renaming the extension.

Keep File Associations Working

A file association is the connection between a file type and the app macOS uses to open it. Changing an extension can affect that association because macOS may identify the file as a different type.

Open One File With a Different App

If the file is valid but opens in the wrong app:

  1. Select the file in Finder.
  2. Choose File > Open With.
  3. Select the app you want to use.

This changes how you open that particular file without changing the default app for all files of that type.

Change the Default App for a File Type

To choose the default app for files with a particular extension:

  1. Select a file in Finder.
  2. Choose File > Get Info.
  3. Expand Open with.
  4. Click the app menu.
  5. Select the app you want to use.
  6. Click Change All.
  7. Confirm the change if macOS asks.

Warning: Change All affects every file with that extension, not just the selected file. Make sure the selected app is appropriate before confirming.

If you only want to use another app once, use File > Open With instead of Change All.

Rename Extensions for Multiple Files

Finder can rename several files at once, but bulk renaming requires care. A mistaken change can affect many files at the same time.

Warning: Before bulk-renaming files, make a backup or duplicate the files. Do not proceed if the files are open or contain unsaved work.

To rename multiple files:

  1. Open Finder and select the files.
  2. Control-click the selection, or click the More button in the Finder toolbar.
  3. Choose Rename.
  4. Use the rename options to replace text, add text, or apply a format.
  5. Review the preview carefully.
  6. Click Rename.

Finder’s bulk rename tools are generally intended for changing filename text. They are not a file-format conversion tool. If you replace extensions across a group of files, make sure every file already uses compatible data.

For a small number of files, renaming them one at a time is safer because you can verify each file’s type and result.

Protect Files Before Making Changes

Before changing an extension, consider these precautions:

  • Make a duplicate of the file in Finder by selecting it and choosing File > Duplicate
  • Keep the original extension until you confirm the renamed file works
  • Close the file’s editing app before renaming it
  • Confirm that the file is not being uploaded, downloaded, synchronized, or actively edited
  • Avoid changing extensions on application files, system files, or files inside app packages
  • Do not delete the original until the renamed or converted copy opens correctly

Renaming a file normally does not delete its contents, but an incorrect extension can prevent apps from recognizing it. Keeping an original copy makes recovery easier.

Troubleshooting

The Extension Is Not Visible

Check Finder’s global setting:

  1. Open Finder.
  2. Choose Finder > Settings.
  3. Select Advanced.
  4. Turn on Show all filename extensions.

If only one file hides its extension, select it, choose File > Get Info, expand Name & Extension, and clear Hide extension.

macOS Does Not Let You Rename the Extension

The file may be locked, located in a read-only folder, or owned by another user or process.

Try the following:

  1. Select the file and choose File > Get Info.
  2. Make sure Locked is not selected.
  3. Confirm that you have permission to modify the folder.
  4. Copy the file to a location you control, such as your home folder, and rename the copy.

Do not change permissions or unlock an important system file unless you understand why it is protected.

The File Will Not Open After Changing the Extension

Restore the original extension:

  1. Select the file in Finder.
  2. Press Return.
  3. Replace the new extension with the original one.
  4. Press Return.
  5. Choose Keep .[old extension] or accept the restored extension if macOS displays a warning.

If you do not remember the original extension, check a backup, another copy, the app that created the file, or the file’s Kind in the Get Info window.

The File Opens in the Wrong App

Use File > Open With to choose an app for one file. If you want all files with that extension to use the same app, use File > Get Info, select an app under Open with, and click Change All.

The Filename Has Two Extensions

A filename such as report.pdf.zip has two suffixes. The final extension is .zip, while .pdf is part of the filename before it.

Rename carefully. If you want a ZIP archive containing a PDF, do not remove .pdf; the complete name should remain something like:

report.pdf.zip

If a downloaded file has an unexpected extension, do not open it automatically. Confirm what it is and whether you trust its source.

The File Name Contains a Period

Only the final extension is normally treated as the filename extension. A file such as:

meeting.notes.docx

has .docx as its extension. The earlier period is part of the filename.

Frequently Asked Questions

Does showing extensions rename my files?

No. Show all filename extensions changes how Finder displays filenames. It does not alter file names or file contents.

Does changing a file extension convert the file?

No. Renaming file.txt to file.docx does not create a Word document. Use an app’s export or conversion feature to create a genuine file in another format.

Should I always show file extensions?

Showing them is useful if you regularly download files, organize documents, troubleshoot file associations, or work with multiple formats. If you prefer a simpler Finder view, you can leave extensions hidden and reveal them for individual files through Get Info.

Why does macOS ask whether I want to use the new extension?

The warning helps prevent accidental changes that could make a file difficult to open. Choose the option that matches your intention. If you are not converting the file and did not mean to change its type, keep the original extension.

Can I change an extension back?

Usually, yes. Rename the file again and restore the original extension. If the file was also modified or converted, restoring the name alone will not restore the original contents.

Will changing an extension change the default app?

It can. macOS may use the new extension to identify the file and select an associated app. You can choose another app with File > Open With or change the default through Get Info.

Can I remove an extension completely?

You can remove the extension from a filename, but doing so may make the file harder for macOS and apps to identify. Keep the extension unless you have a specific reason to remove it.

Final Thoughts

Showing file extensions in Finder makes file types easier to understand and helps prevent accidental renaming mistakes. Use Finder > Settings > Advanced > Show all filename extensions to display them everywhere, or use Get Info to control one file at a time.

When changing an extension, remember that renaming is not conversion. Keep a backup, preserve the original extension until the file works, and use an app’s export or conversion tools when you need a genuine change of format.