File Splitter & Merger
Split any file into numbered parts that fit under a size limit, and merge parts back into one file — verified byte-for-byte in your browser.
Runs in your browser — nothing is uploaded. Verify it
About the File Splitter & Merger
A file splitter that runs entirely in your browser: hand it a file and a size limit, and it cuts the file into numbered parts that each fit under the cap. Give it the parts back and it joins them into the original — then proves the result is identical by checking a SHA-256 checksum written into the manifest.
Every upload, email and messaging limit is a byte count, not a file count. A 2 GB video will not fit under any of them, but 400 MB of parts will — and the parts can be reassembled into a file that is byte-for-byte the original.
How to use the File Splitter & Merger
- Choose split or merge. In split, drop one file and set the part size — the tool tells you how many parts the file will become before you start.
- Split writes the numbered parts and a manifest that lists every part with its SHA-256 digest. Download the parts and keep the manifest with them.
- Merge takes the parts in order, joins them, then recomputes the SHA-256 of the result and compares it to the digest the manifest recorded. A match means the file is identical to the original; a mismatch names the part that changed.
Frequently asked questions
What is a file splitter for?
It breaks one large file into smaller numbered pieces so each piece fits under a limit you actually have to work with: an email attachment cap, an upload form, a messaging app, or a storage quota. You send the pieces, the recipient merges them back into the original. The most common target is 25 MB, the Gmail attachment limit, or 19 MB, the Outlook limit.
Are my files uploaded to a server?
No. Every part is cut and reassembled in your browser from the file you selected. Nothing is sent anywhere — you can disconnect from the network after the page has loaded and the tool still works. That matters here more than on most tools, because the reason people split files is usually that the file is too large or too sensitive to hand to a server.
How do I know the merged file is the original?
The split writes a manifest that records the SHA-256 digest of every part and of the whole file as one value. When you merge, the tool recomputes the digest of the reassembled bytes and compares it to the recorded one. A match is proof the file is identical to the original, not just the same size. If a part was edited, truncated or replaced in transit, the digests differ and the tool tells you which part failed before you rely on the result.
Which part size should I use?
Use a value safely under your limit. If the cap is 25 MB, set the part size to 24 MB so the parts fit in an email with their metadata. The tool converts between MB and KB and shows the resulting part count before you start, so you can see whether 8 MB gives you ten parts or 1 MB gives you forty before committing. For a 2 GB file under a 25 MB cap you get about 82 parts; under a 1 MB cap, roughly two thousand.
Can I merge parts from a different tool?
Yes, as long as you provide the complete set in order. This tool does not use a proprietary container — the parts are plain slices of the original bytes, so any splitter that slices the file the same way produces parts this merger accepts. The manifest only adds the checksum; if you do not have one, the tool merges the parts and simply cannot claim the result is byte-for-byte, because there is nothing to compare against. The parts themselves are not wrapped or encrypted.
What happens if I miss a part when I merge?
The merge fails, not with a silent corruption but with a named error. The tool checks that the part numbers run from 1 with no gaps, that the count matches the manifest, and that the final part ends at the recorded total size. A missing part leaves a gap in the numbering and the tool says which part is absent instead of producing a file that looks complete and is not.
Does it work on large files?
Yes. The file is read and written in chunks, so a multi-gigabyte file does not need to sit in memory at once — peak memory is bounded by the part size, not the file size. Splitting a 4 GB file into 25 MB parts produces one hundred and sixty eight parts and writes about the same total of bytes back to disk. The whole operation is limited by your disk, not by available RAM.
Guides
- File Splitter: Split Into Parts, Merge Back Verified
How to split a file so each part fits a size limit, and how to tell — not claim — that the pieces came back intact.
- File Hash Generator: Verify a SHA-256 Checksum
How to verify a downloaded file against the SHA256SUMS file its publisher ships, without copying one hash out of forty by hand.
- How to Format, Validate, and Minify JSON
Learn how to format, validate, and minify JSON online. A practical guide to working with JSON safely in your browser.