To batch rename selected files in Finder while keeping their file types intact, select the files, Control-click one, choose Rename, and use Add Text or Format for a new naming pattern. Before starting, show filename extensions in Finder so you can see what will remain unchanged. Finder’s built-in batch rename offers replace text, add text, and format options; Apple warns that changing an extension can stop a file opening in its usual app. Apple’s guide to renaming files and guide to filename extensions document these controls and cautions.

Show extensions before selecting files

In Finder, choose Finder > Settings > Advanced, then select Show all filename extensions. Finder normally hides extensions for some files, so displaying them makes the boundary between the editable name and the type suffix visible. For example, Trip-01.jpg has the extension .jpg; if your goal is to rename the photo, keep that suffix intact. Apple notes that showing all extensions overrides individual Hide extension settings, and that extensions identify file types and associated apps. Apple Support: Show or hide filename extensions on Mac

You can also enable Show warning before changing an extension in the same Advanced pane. This adds a prompt if you attempt to change one. The setting is a safeguard, not a guarantee that a rename operation is harmless: inspect the proposed names before confirming, and keep the existing extensions unless you intentionally want to change the file type using an appropriate app. Apple Support: Change Finder settings on Mac

Select only the files you intend to rename

Open the folder that contains the target files and select the specific items. If the files are adjacent in a list, click the first and Shift-click the last to select a range; use Command-click to add or remove individual selections. These selection methods are standard Finder interactions; after selecting, look at the highlighted items and confirm folders or unrelated files have not been included. If you have mixed file types, verify each visible extension before proceeding.

For an extra cautious workflow, start with a small representative group in a folder where the outcome is easy to review. The batch operation changes the selected items’ names; it does not create a copy of each file. If the names are important, preserve a record of the current names or duplicate the files before making a broad change. This is practical risk management rather than a Finder feature Apple promises.

Choose a rename mode that preserves the suffix

Control-click one of the selected files and choose Rename. The Rename Finder Items dialog provides three modes: Replace Text, Add Text, and Format. Apple documents these modes, their input fields, and the final Rename control. For an ordinary batch prefix, suffix, or sequence, Add Text and Format make the intended transformation easier to reason about than editing complete filenames one by one. Apple Support: Rename files, folders, and disks on Mac

Add a prefix or suffix

Choose Add Text, enter the text to insert, then choose whether to add it before or after the current name. For instance, adding ProjectA_ before a set of names such as notes.txt and image.jpg would produce names conceptually like ProjectA_notes.txt and ProjectA_image.jpg; the extension remains part of the existing name. Adding text after the name is useful for a label, but check the preview carefully so the added text appears before the extension rather than changing the suffix. If the dialog’s preview does not show the outcome you intend, cancel and choose another method.

Create a numbered set

Choose Format to give the selected files a consistent name and an index, counter, or date. Enter a base name in Custom Format, choose where the sequence element goes, and set the starting number when that option is available. For a set of scans, a base such as Receipt with a counter can produce an ordered series while retaining each file’s extension. The exact resulting names depend on the format choices and current dialog; use the preview as the authority before applying. Apple documents the name format choices and starting-number field, but does not describe a separate setting to rewrite file extensions in this workflow.

Replace a repeated text fragment

Choose Replace Text when the existing names share a fragment that should change. Enter the text to find and the replacement text in the corresponding fields. This mode is appropriate for correcting or standardizing a repeated label, but it can affect every match within the selected names. Avoid a broad search string that could remove or replace part of an extension; with extensions visible, check the proposed results for the original suffix on each item.

Review the result before clicking Rename

The most useful safety check is a name-by-name comparison: confirm that each selected file has the desired base name, any number appears in the intended position, and the original extension is still present. If a .pdf file now appears to end in .txt, stop and cancel rather than accepting a changed type. Apple cautions that changing the extension may prevent the file from opening in the app used to create it. Changing a filename suffix does not itself convert the underlying file format; Apple recommends using the app that created the file for format conversion. Apple Support: Show or hide filename extensions on Mac

Once the preview looks correct, click Rename. Then review the resulting names in Finder and open a representative file if that is appropriate for your task. A successful rename means the names changed; it does not mean a file’s contents or format changed. If a name is wrong, Finder does not document a universal “undo batch rename” guarantee in the rename instructions, so do not rely on undo as your recovery plan. Keep your original-name record or duplicate available until you have confirmed the results.

Common problems and how to avoid them

The extension is not visible. Turn on Show all filename extensions under Finder > Settings > Advanced. Some names may still not behave as expected because Apple says the setting affects most, but not all, filenames; for an individual item, use File > Get Info or Command-I, expand Name & Extension, and check its Hide extension setting. Apple Support: Show or hide filename extensions on Mac

The menu item or dialog option differs. macOS versions can present interface details differently, but Apple’s documented Finder batch rename choices are replacing text, adding text, and changing the name format. If an option you expect is absent, use those documented controls rather than assuming Finder has a command for it. Apple’s guide does not describe a dedicated “keep extension” toggle; the practical safeguard is to keep the extension visible, use a mode that changes the base name, and inspect the preview.

You need a different file format. Do not rename .png to .jpg or .txt to .rtf as a substitute for conversion. Apple says to use the app that created the file to change its format, with TextEdit and Preview given as examples for certain conversions. Whether conversion is supported depends on the app and source file. Apple Support: Show or hide filename extensions on Mac

A simple decision rule

Use Add Text to place a shared label before or after existing names, Format to create a consistent base name with an index, counter, or date, and Replace Text to swap a repeated fragment. In each case, expose extensions first, select a limited and correct group, inspect the preview, and only then apply the change. This small sequence makes the file-type suffix visible at the moment when it matters.

Wallo’s Mac workflow library focuses on arranging existing open windows and to-dos locally by goal, with keyboard focusing. It may be useful for keeping a Finder window and related task in view while you work, but Finder itself performs the file renaming described here.

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