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How to find duplicate files on a Mac
By Himanshu Ranjan · Updated 8 November 2026
Select the folder in Finder, open FileDial and choose Batch › Find duplicates. It writes a report listing identical files and deletes nothing, so you review the report and remove the extra copies yourself in Finder. It runs offline on your Mac and compares content, not just names.
What the tool does
Batch › Find duplicates is listed for folders and files, and its note is exact: it writes a report; nothing is deleted. That is a deliberate stance. A duplicate finder that deletes is a way to lose a file you needed.
You read the report, check the paths, and remove what you choose in Finder.
Steps
Use it on a copy of a messy folder first if you are nervous.
- Select the folder in Finder.
- Open the dial with the right Option key and choose Batch, then Find duplicates.
- Open the report and look at each group.
- Delete copies in Finder yourself, keeping the one in the right place.
How duplicates are found
The general technique behind duplicate detection is hashing: passing a file's contents through a hash function gives a content address, and identical files produce identical addresses. Wikipedia describes this for content-addressable storage and version control. Same name does not make a duplicate, and different names do not make a unique file.
Related tools: Batch › Checksums (SHA-256), Batch › Checksums (MD5), Batch › Checksums (SHA-1) and Batch › Checksums (SHA-512) write a text file of checksums, so you can compare files yourself. Of those, MD5 collisions can be computed within seconds and SHA-1 is considered broken, so prefer SHA-256 when it matters.
Photos and look-alikes
Exact-copy finders miss near-duplicates, such as a burst of similar photos. Batch › Find similar and blurry photos writes a CSV report and copies suggested rejects to a folder, again with nothing deleted. For spreadsheet rows, Data › Remove duplicate rows keeps the first of each identical row.
When the problem is a folder tree with the same file in many subfolders, Batch › Flatten folder can copy everything into one folder to make clutter easier to see.
What macOS offers
Finder can show duplicates only by eye. In some Finder views, sorting by name and size can reveal obvious copies,. For arbitrary folders there is no built-in finder, which is why a report tool is useful.
Deciding which copy to keep
When the report shows two or more identical files, keep the one in the most meaningful place, such as the project folder rather than Downloads. Look at the folder names. Look at the dates: the older creation date is often the original. Do not delete copies that other things point to, such as a photo library's originals or a project's linked assets.
A safe way to clear them is to move, not delete: create a folder called Duplicates to check, drag the extra copies there with Share › Move to… and wait a week before emptying. If nothing broke, then delete.
Common mistakes and when FileDial fits
A duplicate in the sense of this tool means identical content. Two photos of the same scene, a resized copy of an image, or a PDF saved twice with different compression will not match. Batch › Find similar and blurry photos handles near-duplicates for photos. For documents, Combine › Compare two files writes a unified .diff plus a side-by-side .html so you can see how two versions differ.
Large libraries take time to hash. Start with a single folder, such as Downloads or Documents, before running on a whole drive.
It is right if you want a report first, deletion by your own hand, and no uploads. It is not a one-click cleaner, and that is deliberate.
If you need automation, run it on one folder, review, and repeat. For photo libraries managed by an app, avoid touching the library package directly; export or review inside the app instead, because removing files from a managed library can break it.
Deleting both copies is the nightmare scenario, so always keep one. Second is deleting from a managed library such as the Photos library, where files are stored inside a package and deleting them from outside can break the library. Third is trusting names: two files with the same name can differ, and files with different names can be identical. Fourth is running it on a whole drive first, which takes time and produces an overwhelming report.
Start small: Downloads, then Desktop, then a project folder. Fix one area at a time.
If your Mac is short of space, sort the report by group size and start with the largest files, since removing one big duplicate saves more than a hundred tiny ones. Batch › Folder size report writes a text report of sizes, and Batch › Compressed size report writes a table of raw, gzip, Brotli and LZFSE sizes per file, which shows what compression could save.
Questions
Does Find duplicates delete anything?
No. Batch › Find duplicates writes a report and nothing is deleted, according to the tool's note. You read the report, decide which copy to keep, and remove the extras yourself in Finder. That makes it safe to run on a folder you care about.
How are duplicates detected?
Duplicate detection in general compares file content by hashing: passing a file through a hash function gives a content address, and identical files give identical addresses. Wikipedia describes this for content addressing and deduplication. Names and dates do not matter, only the content does.
Can it find near-identical photos, not just exact copies?
Not this tool. Batch › Find similar and blurry photos writes a CSV report and copies suggested rejects to a folder, with nothing deleted. That is the tool for bursts of similar shots, while Find duplicates is for byte-identical copies.