How to see what is inside an archive on a Mac without extracting it

Why look first

An archive that arrived by email or download may be large, may hold more than you expected, or may be damaged. Extracting blindly fills a folder with files you did not want.

Extract › List contents writes a text listing and nothing is extracted. That gives you names to read, and you can search them with any editor.

Steps

The same steps work for any archive FileDial lists.

1. Select the archive in Finder.
2. Open the dial with the right Option key and choose Extract, then List contents.
3. Open the text file that appears beside the archive.
4. If the names look right, choose Extract › Extract here.

Testing integrity

A listing does not prove the data is good. Developer › Test archive integrity writes a report named OK or FAILED, with nothing extracted. That is the quick check after a large download or transfer.

For a download with a published checksum, Developer › Verify checksum… writes a report named OK or MISMATCH and picks MD5, SHA-1, SHA-256 or SHA-512 by length. A cryptographic hash makes it practical to detect changes to a file, though non-cryptographic checksums only catch accidental ones.

Built-in alternative

Finder's Archive Utility extracts on double-click, and Apple's guide describes no preview of contents. You can see a ZIP's contents in Terminal with the unzip -l command, which lists without extracting, but it is a command-line habit and works for ZIP only.

A tool that lists any supported archive from the dial saves the detour.

A safety habit

Archives are a common way to deliver malware. Reading a listing, testing integrity and, for software, running Developer › Check signature and notarization on the archive before opening anything is a sensible routine. None of it needs an upload.

Reading the listing

The listing is a plain text file, so use your editor's search. Look for surprises: executable files inside an archive that claims to hold photos, huge files where you expect small ones, or paths that start with unexpected folder names. A listing cannot prove a file is safe, but it shows whether the archive matches what you were told.

Check the file count and rough sizes against the sender's description. If the sender promised twelve files and you see two thousand, stop and ask before extracting.

Common mistakes and when FileDial fits

If the listing looks right, run Extract › Extract here, which puts the contents in a folder named after the archive. For installers, the note on one Extract tool says installer packages are expanded with their payloads, so read what is inside before running anything. For a disk image, Extract › Extract disk image mounts it read-only, copies the contents into a folder and unmounts.

If you are the sender, the same listing is a useful last check before you send. List your own ZIP, confirm that no private file slipped in, and only then share it.

It is a quick local check that fits in the same dial as Extract. If you only use ZIPs and are comfortable in Terminal, unzip -l lists contents with no extra software.

What the dial adds is the same behaviour for archives it lists, plus a one-step integrity test and a checksum verifier, without typing commands. None of it needs a connection, and nothing leaves your Mac.

Assuming that a clean listing means a safe archive is the main one. A listing shows names, not intent. Another is skipping the integrity test for large downloads, where truncation is common. A third is confusing a listing with a preview of the content. A fourth is extracting before listing when you are short on disk space, which can fill your drive with something you did not want.

Finally, make a habit of listing your own archives before sending them. It takes a few seconds and catches a stray private file that you did not mean to include.

Related checks, all local: Developer › Verify checksum… for downloads, Developer › Check signature and notarization for software archives, and Batch › Folder size report to see what is large in a folder before you archive it.

One more habit worth building: when you create archives for others, add the listing to your message. Pasting the text file into an email lets the recipient confirm what they received. For formal deliveries, Archive › Deliverable package… builds a ZIP with a README.txt and a SHA-256 manifest inside, plus the ZIP's own .sha256 file, which is an even stronger way to say what was sent.

Questions

Sources

1. Wikipedia: ZIP (file format)
2. Wikipedia: Cryptographic hash function
3. Apple Support: Zip and unzip files and folders on Mac

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