Choose ZIP or 7z
Choose ZIP when you want a straightforward way to send ordinary files to someone whose archive software you do not know. Consider 7z when the recipient can open it and your own test shows a useful size reduction. For password-protected files, check the encryption support of both applications as well as the format.
Start with the recipient
An archive is useful only if the person receiving it can get the files out. macOS includes ZIP compression and extraction, and Apple's Files app can create and open ZIPs on iPhone and iPad.
That makes a conventional, unencrypted ZIP a practical default for a folder of documents. It does not mean that every ZIP compression or encryption method works in every built-in reader.
For 7z, ask which application the recipient uses. The project's recorded macOS 26.2 check found that Archive Utility extracted an unencrypted 7z, but that result is not a compatibility guarantee for every OS version or 7z variant. See opening 7z on Mac for the tested workflow and limits.
Match the format to the job
| Your task | Starting choice | What to check |
|---|---|---|
| Send ordinary documents without arranging another app | ZIP | Open the result with the recipient's expected tool |
| Reduce the size of a folder before transfer | Compare ZIP and 7z | Actual output sizes and the time needed to create and extract each |
| Send password-protected files | An encryption scheme supported at both ends | The format name alone is insufficient |
| Browse, extract selected files or edit locally in Kernir | ZIP or 7z | Whether the specific archive uses supported methods |
Neither format changes a document into another type. A spreadsheet inside a ZIP or a 7z remains a spreadsheet after extraction. The archive groups the files and may compress their stored data.
Test compression on your files
There is no useful universal promise that one archive will be a fixed percentage smaller. The result depends on the contents and compression settings. A folder of similar text files can behave very differently from a collection of already compressed media.
You can make a small comparison using the Mac's libarchive-based tar. In Terminal, go to the directory containing a folder called Project. Choose output filenames that do not already exist, then run:
tar --format zip -cf "Project-test.zip" "Project"
tar --format 7zip -cf "Project-test.7z" "Project"
ls -lh "Project-test.zip" "Project-test.7z"
The listing shows the resulting file sizes. These commands create unencrypted archives. They compare the defaults of this particular tool; they are not a benchmark of every ZIP or 7z implementation, nor a measurement of Kernir's performance.
Before choosing the smaller result, also try extracting it with the tool the recipient will use. If the size saving is negligible, compatibility may matter more than compression. Keep the original folder until both results have been checked.
Encryption belongs to the workflow
The 7z format supports AES-256 encryption and solid compression. An application's support for 7z does not automatically mean it supports all those features.
Kernir reads and writes 7z with or without AES-256 encryption. Encrypted 7z output includes encrypted headers, so the password is needed to list its filenames. It supports common encrypted ZIPs, with limits explained in the password-protected ZIP guide.
When sharing an encrypted archive, agree on a compatible reader and test a small example first. Changing the extension or converting to a format that cannot preserve the encryption is not a substitute for choosing the right settings.
Choose the format in Kernir
Kernir can create and edit ZIP and 7z archives, including their supported password-protected variants.
The Mac download is coming soon. You can view the source and build instructions on GitHub. These steps describe the current app workflow.
Choose File › New (⌘N), add the files and save. Select ZIP or 7z in the Format control. For an archive you already have, File › Save As… (⇧⌘S) creates a copy in the selected format.
Kernir also reads RAR, but RAR is not an output format. If you need to send a ZIP copy of a RAR, follow the RAR-to-ZIP conversion guide.
The ZIP and 7z samples let you test format and password compatibility. Their tiny text payload is not a compression benchmark; use your own representative files for size comparisons.
Kernir.dmg, signed and notarized. Requires macOS 14 or later.
Related guides
App steps were checked against current source code. Updated .
Current encryption support was rechecked against source code on . Mobile screenshots, where shown, were supplied by the project owner.
