Question 1

What does the File Merger do?

Accepted Answer

It rejoins split file parts (.001, .002, ...) back into the original file. Parts are auto-sorted by their extension number, then concatenated in order. If you provide a manifest file (.sha256 from the splitter), each part is verified with CRC32 + SHA-256 before merging.

Question 2

How does auto-detection work?

Accepted Answer

Drop multiple files ending in .001, .002, .003, etc. The merger parses the numeric extension and sorts them. It detects the base name (everything before the .001), so you can drop parts with any naming pattern (myfile.001, myfile.002, ...). Missing parts in the sequence are flagged before merging.

Question 3

What if I don't have the manifest?

Accepted Answer

You can still merge without a manifest — the merger will simply concatenate the parts in order. However, without the manifest, integrity (CRC32 + SHA-256) cannot be verified. We recommend keeping the .sha256 manifest file from the splitter.

Question 4

What's HJSplit format?

Accepted Answer

HJSplit is a popular cross-platform file-splitter. It names parts by appending a sequential 3-digit extension (.001 for part 1, .002 for part 2, etc.). This merger reads that format natively. 7-Zip also rejoins HJSplit parts (right-click .001 → 7-Zip → Extract here).

Question 5

What extra features does this tool have?

Accepted Answer

10 extras: (1) Drag-drop multiple parts. (2) Auto-sort by extension number. (3) Progress bar during merge. (4) Checksum verification (CRC32 + SHA-256). (5) Stats (parts count, merged size, verification result). (6) Preview merged file info. (7) Custom output filename. (8) Missing part detection. (9) History (localStorage — last 10 merges). (10) Shareable URL with settings.

Question 6

Are my files uploaded anywhere?

Accepted Answer

No. All merging runs in your browser using ArrayBuffer concatenation. Your files never leave your device.

File Merger

How to use