How to Open 001 Files or Extract 001 Files with 7-Zip or HJSplit File Joiner. If you've encountered files with numbered extensions like .001, .002, .003, etc., you're dealing with a split archive. These files are fragments of a larger file, divided using a file splitter to make massive files easier to share, store, or transfer.
Each numbered file represents part of the complete data set. To access the full content, these parts must be joined and then extracted using tools such as 7-Zip or HJSplit.
Once combined, the output might be an ISO image, a BIN/CUE file pair, installation folders, or even a complete executable (.exe) file.
One major reason for splitting large files is file system compatibility. For example, drives using the FAT32 file system cannot store individual files over 4GB. Splitting allows large files to bypass this limitation.
Pro Tip: The .001 file contains essential data that tells your file joiner tool how to reassemble the full archive. Without it, extraction is impossible.
What Is a .001 File?
A file with a .001 extension is the first part of a multi-part archive created using tools such as 7-Zip, HJSplit, or WinRAR. These files are not functional by themselves and must be combined with the rest of the parts to form a complete file.
What Is a File Joiner?
A file joiner is a specialized utility designed to reassemble files that have been split into smaller segments—typically with extensions like .001, .002, .003, and so on. These tools scan the sequence of split files and reconstruct them into one complete, usable file.
When dealing with large file downloads, backups, or archives split for compatibility (e.g., FAT32 drives), a file joiner is essential for merging the data back together.
Key Features of File Joiner Tools:
- Automatically detects and processes sequential file parts (.001, .002, etc.).
- Reconstructs the original file with no data loss.
- Some tools also verify file integrity or support checksum comparison.
- Most work without requiring installation and are lightweight.
Popular File Joiner Tools:
- HJSplit – A simple, portable joiner/splitter with no installation required. Ideal for Windows systems.
- 7-Zip – While mainly an archiver, it can extract and join .001 files automatically if the archive was created with 7-Zip.
- FFSJ (Fast File Splitter & Joiner) – Another lightweight alternative for quickly merging split files.
Note: A file joiner only reassembles the split parts. Once joined, you may still need to extract or mount the resulting file depending on its format (e.g., ISO, BIN, or ZIP).
How Split Archives Work
- Large files are divided into smaller segments with extensions like .001, .002, .003, and so on.
- All segments must be present to reassemble the original file correctly.
- The extraction process begins with the .001 file.
- The software detects and merges the remaining parts automatically.
Note: These are not regular ZIP or RAR archives and require special software to open and extract properly.
How to Open .001 Files Using 7-Zip
One of the easiest and most reliable methods to open and extract .001 files is with the free tool 7-Zip.
- Download and install 7-Zip.
- Navigate to the directory containing your .001 file.
- Right-click the .001 file and choose 7-Zip > Extract Here.
- 7-Zip will automatically detect and join the remaining parts (.002, .003, etc.) to extract the full archive.
TIP: Make sure all parts are in the same folder and named sequentially for successful extraction. If the original file is an ISO or BIN, you can burn it using CD/DVD software or mount it with a virtual drive.
How to Join .001 Files Using HJSplit
If 7-Zip doesn’t work or you prefer another option, HJSplit is a dedicated file splitter and joiner tool that can be ideal to use to join 001 files.
- Download HJSplit, unzip the folder, and run the tool.
- Click "Join" in the main menu.
- Select the .001 file as the Input File.
- Choose a destination and name for your Output File.
- Click "Start" to begin joining.
- Once complete, locate the merged file in your output folder.
As long as all segments are in the same folder, HJSplit will automatically recognize and combine the .002, .003, and other parts.
Frequently Asked Questions
What is a .001 file?
A .001 file is part of a split archive. It’s typically the first piece of a larger file divided into multiple parts using tools like 7-Zip or HJSplit for easier file management and sharing.
Can I open .001 files without the other parts?
No. All sequential parts (.002, .003, etc.) are needed. Without them, the file cannot be fully extracted or reconstructed.
How do I open 001 files using 7-Zip?
Install 7-Zip, right-click the .001 file, and select Extract Here. Ensure all other parts are present in the same folder.
Can HJSplit open or join .001 files?
Yes. HJSplit is specifically designed to join split files like .001. It will automatically detect related parts and reconstruct the full file.
Are .001 files safe?
They’re generally safe if sourced from a reputable location. Still, it’s best practice to scan them with antivirus software before extracting.
What happens if the .001 file is missing?
You won't be able to extract or join the archive. The .001 file is required to initialize the process and reference the rest of the split files.
What if 7-Zip doesn’t recognize the .001 file?
Ensure:
- All parts are present and named correctly.
- The archive was created using 7-Zip or a compatible tool.
- Try HJSplit if 7-Zip fails or re-download the archive if it’s corrupted.
Final Thoughts: Open 001 Files Easily
Opening or extracting .001 files doesn’t have to be complicated. With the right software and all parts in place, the process is straightforward. Whether you choose 7-Zip for extraction or HJSplit for joining:
- Always keep all parts (.001, .002, etc.) together in the same folder.
- Start with the .001 file for extraction or joining.
- Use trusted tools like 7-Zip or HJSplit.
With these simple steps, you’ll have no trouble opening, extracting, or converting split archives. Now you know exactly how to open 001 files the right way!