7z 形式
7zファイルのすべて
圧縮
はい
解凍
はい
拡張子
.7z
プラットフォーム
All
7zとは？
A 7z file is a compressed archive format developed by Igor Pavlov for 7-Zip. It uses the LZMA or LZMA2 compression algorithm, which typically achieves 30-50% better compression than the ZIP format's deflate algorithm.
7z supports advanced features including AES-256 encryption with filename encryption, solid archives (compressing multiple files together for better ratio), split volumes, and self-extracting archives.
The 7z format is open source and has been adopted by many other projects. It supports multiple compression methods (LZMA, LZMA2, BZIP2, PPMD) and can be opened by most modern archive software.
7-Zipで7zを開ける？
7-Zip is the native creator of 7z format — full read and write support with all features.
7-Zip can create 7z archives with LZMA2 compression, AES-256 encryption, filename encryption, solid archives, and split volumes.
7-Zip supports all 7z compression levels from Store (no compression) to Ultra (maximum compression with largest dictionary).
7-Zip can create self-extracting 7z archives (.exe) that extract without 7-Zip installed.
7zの解凍方法
Right-click the 7z file
In Windows Explorer, locate your .7z file, right-click it, and navigate to the "7-Zip" context menu.
Choose extraction option
Select "Extract Here" to extract in the current folder, or "Extract to [folder name]\" to create a subfolder.
Enter password if required
If the 7z archive is encrypted, 7-Zip will prompt for the password. If filenames are encrypted, you'll need the password even to see the file list.
Access your files
Once extraction completes, your files are ready in the destination folder with the original directory structure preserved.
7zの作成方法
Select files to compress
Select the file(s) or folder(s) you want to add to the 7z archive in Windows Explorer.
Open the archive dialog
Right-click the selected files, choose "7-Zip" > "Add to archive..." to open the creation dialog.
Choose 7z format and settings
The default format is 7z (recommended for best compression). Set the compression level (Normal, Maximum, Ultra) and method (LZMA2 recommended).
Enable solid archive (optional)
For many small similar files, enable "Create solid archive" for better compression ratio. Solid archives compress all files as a single data stream.
Create the archive
Click OK. 7-Zip creates the .7z file with the best possible compression ratio.
7zのパスワード保護
7z format supports AES-256 encryption with an optional "Encrypt file names" feature that hides the contents list entirely.
To add a password: in the "Add to archive" dialog, enter a password in the Encryption section and check "Encrypt file names" for maximum privacy.
7z is the only format that supports filename encryption in 7-Zip — ZIP does not support this feature.
7z 仕様
| 拡張子 | .7z |
| 圧縮 | LZMA, LZMA2, BZIP2, PPMD, Deflate, Store |
| 暗号化 | AES-256 (with filename encryption) |
| プラットフォーム | All (with 7-Zip or compatible software) |
| 最大サイズ | 16 Exabytes |
| 開発者 | Igor Pavlov |
| MIME Type | application/x-7z-compressed |
7zのよくあるエラー
Cannot open 7z file
原因: No compatible software installed.
解決策: Install 7-Zip from 7-zip.org. Windows cannot open 7z files natively. Other archivers like WinRAR, PeaZip, and NanaZip also support 7z.
7z extraction fails with CRC error
原因: Archive corruption from incomplete download or storage error.
解決策: Re-download the file. Use 7-Zip's "Test" function to verify integrity. 7-Zip can extract healthy files from partially corrupted archives.
7z file won't extract — wrong password
原因: Incorrect password for encrypted archive.
解決策: 7z encryption (AES-256) cannot be bypassed. You must have the correct password. If filenames are encrypted, the password is needed even to view the list.
7z vs 7Z
| Feature | 7z | 7z |
|---|---|---|
| Compression ratio | Best (LZMA2) | Best (LZMA2) — same format |
| Filename encryption | Yes | Yes — this IS 7z |
| Solid archives | Yes | Yes |
| Split volumes | Yes | Yes |
| Open source | Yes (LGPL) | Yes |
7z FAQ
What is a 7z file?
A 7z file is a compressed archive format created by 7-Zip. It uses LZMA/LZMA2 compression for high compression ratios and supports AES-256 encryption, solid archives, and split volumes.
How to open 7z files?
Install 7-Zip (free) from 7-zip.org, then right-click the .7z file and select 7-Zip > Extract Here or Extract to folder. Other archivers like WinRAR and PeaZip also support 7z.
Can Windows open 7z natively?
No, Windows cannot open 7z files without additional software. You need to install 7-Zip, WinRAR, PeaZip, or another compatible archiver.
Is 7z better than ZIP?
For compression ratio and security, yes — 7z typically achieves 30-50% smaller files and supports filename encryption. For compatibility, ZIP is better as it opens natively on all systems.
Can Mac open 7z files?
macOS cannot open 7z natively. Install The Unarchiver, Keka, or p7zip (via Homebrew) to open 7z files on Mac.
Can Linux open 7z files?
Yes, install p7zip or 7zip package (sudo apt install p7zip-full). Most GUI archive managers support 7z extraction once the package is installed.
What is a solid archive?
A solid archive compresses all files as a single data stream rather than individually. This improves compression ratio for many small similar files but means any corruption affects all files.
Can 7z encrypt filenames?
Yes. 7z is the only format in 7-Zip that supports encrypting filenames. When enabled, the file list is completely hidden until the correct password is entered.
What is the maximum 7z file size?
7z supports archives up to 16 Exabytes and individual files up to 16 Exabytes. In practice, you are limited by your filesystem and available storage.
Is 7z open source?
Yes. The 7z format is open source under the GNU LGPL license. The compression algorithms (LZMA/LZMA2) are also open source and used by many other projects.
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