How to Change a File Extension Batch on a Mac

Written by amy marie
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How to Change a File Extension Batch on a Mac
Macintosh computer (mac background image by haruspex from

Surprisingly, Mac OS X does not contain a simple Finder command to change the file extension for a group of files in one step as a batch process. If you only have a few files to rename, doing that one file at a time is not a problem. However, when you have a large number of files to rename, the job becomes quite tedious and you yearn for an easier way. By using Automator, a free application included with Mac OS X, you can create your own automated workflow to batch rename files.

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Things you need

  • Mac OS X version 10.6 or higher

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  1. 1

    Open the Automator application. You can find Automator in your Applications folder.

  2. 2

    Select "New" from the File menu and choose the "Workflow" template. The Automator workspace opens. The workspace displays a library of Automator actions on the left side and an area to build your workflow on the right.

  3. 3

    Drag the action "Get Selected Finder Items" onto the workflow area at the right side of the workspace.

  4. 4

    Drag the action "Rename Finder Items" onto the workflow area. Automator displays a warning sheet to let you know that this action will change the file names and offers to include a "Copy Finder Items" action in your workflow. You may want to add this action to your workflow for safety when you create it; you can remove it later after you test the workflow. Automator adds a "Copy Finder Items" action and an "Add Date or Time to Finder Item Names" action to your workflow.

  5. 5

    Choose "Replace Text" in the pop-up menu at the top of the "Add Date or Time to Finder Item Names" action. The action name changes to "Replace Text in Finder Item Names."

  6. 6

    Fill in the text replacement parameters. In the box labelled "Find," type in the current file extension. In the pop-up next to it, select "extension only." In the box labelled "Replace," type in the new file extension.

  7. 7

    Select "Save" from the File menu and assign a name to your workflow.

  8. 8

    Test your workflow. Select the files you want to change and then click "Run" in the toolbar. The file names change according to your specifications.

Tips and warnings

  • Save your workflow as an application if you want to run it by double-clicking it, rather than running it from Automator.
  • If including a "Copy Finder Items" action in your workflow causes it to rename the files improperly, simply delete that action from the workflow.

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