7Z (7-Zip) is an open-source archive format that achieves the highest compression ratios among common archive formats. Created by Igor Pavlov in 1999, the format uses the LZMA and LZMA2 compression algorithms which consistently outperform ZIP's Deflate and often beat RAR's proprietary compression. If you need maximum compression to save storage space or reduce download times, 7Z is the format to use.
AnExplorer opens 7Z archives from internal storage, SD cards, USB OTG drives, network shares, and cloud folders. You can browse inside a 7Z file, extract individual files, or unpack the entire archive. AnExplorer also creates 7Z archives directly on your Android device.
Quick Answer
Open AnExplorer, find the .7z file, and tap it to browse inside. Long-press the archive and choose Extract if you want the files in a regular folder. To create a 7Z archive, select files and tap Compress → 7Z.
What Is a 7Z File?
A 7Z file is a compressed archive container that stores one or more files using high-efficiency compression algorithms. The format is part of the 7-Zip project, which is free and open-source software released under the LGPL license. This means anyone can create, extract, or build tools for 7Z files without licensing fees — unlike RAR which requires a WinRAR license for creation.
Key characteristics of the 7Z format:
- Open architecture — supports pluggable compression methods
- High compression ratio — LZMA2 typically achieves 30-70% better compression than ZIP
- Solid compression — compresses similar files together for even smaller archives
- Large file support — handles files up to 16 exabytes theoretically
- AES-256 encryption — strong password protection for sensitive data
- Unicode filenames — full international character support
- Header compression — even the archive metadata is compressed
Where You Encounter 7Z Files
You will come across 7Z files in these common scenarios:
- Open-source software — many projects distribute source code and binaries as .7z
- Large file downloads — forums and file hosts use 7Z for maximum compression
- Backup archives — created by 7-Zip on desktop for efficient storage
- Developer tools — SDKs, libraries, and toolchains often ship as .7z
- ROM and firmware files — custom Android ROMs and firmware packages
- Game assets — texture packs, mods, and fan translations
- Data archiving — long-term storage where size savings matter
How to Open 7Z Files with AnExplorer
Browse Without Extracting
- Launch AnExplorer
- Navigate to the folder containing your
.7zfile - Tap the file — the archive viewer opens
- Browse the contents like a normal folder structure
- Tap individual files to preview them (images, documents, text)
Extract the Entire Archive
- Navigate to the
.7zfile in AnExplorer - Long-press the file to select it
- Tap the menu (⋮) → Extract
- Choose a destination folder
- Tap OK — extraction begins
- Enter password if the archive is encrypted
Extract Selected Files
- Tap the
.7zfile to open the archive viewer - Navigate to the files you need
- Long-press to select specific files
- Tap Extract → choose destination
- Only the selected files are extracted
How to Create 7Z Files with AnExplorer
AnExplorer can create 7Z archives directly on your device:
- Navigate to the files or folders you want to compress
- Long-press to select them (multi-select with checkboxes)
- Tap the menu (⋮) → Compress
- Choose 7Z as the format
- Name your archive
- Optionally set a password for encryption
- Tap OK — the archive is created in the same folder
Technical Details
Compression Algorithms in 7Z
The 7Z container supports multiple compression methods:
| Algorithm | Best For | Compression | Speed |
|---|---|---|---|
| LZMA | General-purpose | Excellent | Moderate |
| LZMA2 | Multi-threaded, large files | Excellent | Faster than LZMA |
| PPMD | Text and source code | Superior for text | Slow |
| BZip2 | Compatibility | Good | Moderate |
| Deflate | ZIP compatibility | Good | Fast |
AnExplorer uses LZMA2 by default when creating 7Z files, providing the best balance of compression ratio and extraction speed.
Solid vs Non-Solid Archives
7Z supports two archive modes:
- Solid archive — files are compressed together as one continuous data stream. This produces smaller archives when files have similar content (like a folder of documents or source code). The trade-off is that extracting a single file requires processing all preceding files.
- Non-solid archive — each file is compressed independently. Slightly larger archives but faster random access to individual files.
Dictionary Size
The LZMA/LZMA2 dictionary size determines how much data the algorithm remembers during compression:
- Larger dictionary = better compression for large files
- 7Z supports dictionary sizes from 64 KB to 1.5 GB
- Archives created with very large dictionaries (256 MB+) need significant RAM during extraction
- On mobile devices with limited RAM, extraction of such archives may be slower
Encryption
7Z uses AES-256 encryption when a password is set:
- The entire file data is encrypted
- Optionally, file names can also be encrypted (hides the archive contents list)
- Without the correct password, nothing about the archive contents is revealed
- The encryption is considered very strong — brute-forcing AES-256 is computationally infeasible
7Z vs ZIP vs RAR
| Feature | 7Z | ZIP | RAR |
|---|---|---|---|
| Compression ratio | Best | Good | Very good |
| Compression speed | Slow | Fast | Moderate |
| Extraction speed | Moderate | Fast | Fast |
| Open format | ✅ Free (LGPL) | ✅ Open standard | ❌ Proprietary |
| Create on Android | ✅ | ✅ | ❌ (needs license) |
| Universal support | Moderate | Excellent | Good |
| Encryption | AES-256 | AES-256 (modern ZIP) | AES-256 (RAR5) |
| Solid archives | ✅ | ❌ | ✅ |
| Recovery records | ❌ | ❌ | ✅ |
| Self-extracting | ✅ (Windows) | ✅ (Windows) | ✅ (Windows) |
When to use 7Z: Maximum compression for archiving or when file size matters most. When to use ZIP: Sharing files with anyone (universal compatibility). When to use RAR: When you receive RAR files from others (cannot create on Android).
Use Cases
- Archiving large folders — 7Z's superior compression saves significant storage on your device
- Creating encrypted backups — AES-256 ensures sensitive files remain private
- Compressing before sharing — smaller files transfer faster over mobile networks
- Receiving developer packages — open-source software and SDKs frequently ship as .7z
- Reducing app backup size — compress exported APKs and data for efficient storage
- Storing media collections — photos and documents compress well in 7Z solid mode
Troubleshooting
Extraction is extremely slow
- 7Z archives with large dictionary sizes (512 MB or 1 GB) require substantial RAM. On devices with 3-4 GB RAM, extraction may swap and slow down considerably.
- Solid archives must process all data sequentially. A 5 GB solid archive will take several minutes even on flagship devices.
- This is normal 7Z behavior — the trade-off for high compression is slower extraction.
"Not enough memory" error
- The archive was created with a dictionary size exceeding your device's available RAM.
- Close other apps to free memory and try again.
- As a last resort, extract on a PC and transfer the files to your device.
Cannot open password-protected 7Z file
- 7Z passwords are case-sensitive. Verify exact capitalization.
- If file names are encrypted, AnExplorer shows a password prompt before displaying any contents.
- There is no password recovery for 7Z — if you forget the password, the data is inaccessible.
Corrupted 7Z file
- Unlike RAR, 7Z does not include recovery records. A corrupted 7Z file usually cannot be repaired.
- Re-download the file from the source.
- Check if the download completed fully — partial downloads produce corrupt archives.