File Splitter & Joiner

Split large files into smaller parts by size and rejoin them - all in the browser.

Tested tool guide Tested browser tools Checked August 16, 2026

What File Splitter & Joiner does and how it behaves

File Splitter & Joiner turns one selected file into an ordered set of size-limited binary fragments, then reconstructs the source when every fragment is supplied in sequence. It is intended for moving or storing a file where the whole file exceeds a per-file limit. Splitting does not compress, decode, or convert the format; it separates the byte stream. The common surprise is that a fragment is usually not a usable document, archive, video, or image by itself. Processing stays in the browser, so the selected bytes are not uploaded.

How the result is produced

Splitting the source

After selecting the source, set the maximum amount of data allowed in one part. The splitter emits consecutive portions in source order until every byte is represented. Each full portion reaches the selected limit, while the final portion holds the remainder and may be smaller. The complete numbered set, not any single portion, represents the original file, so preserve the sequence.

Rejoining every part

To join, supply the parts created from one source and ensure their original order. Reconstruction places the contents of the first part immediately before the second, followed by every remaining part. Exact recovery is not possible when a part is missing, duplicated, changed, or taken from another split set. Keep or restore the source filename extension so applications can identify the reconstructed format.

Good uses

Breaking a disk image, database export, or other large binary file into pieces that fit a destination's per-file limit.
Dividing a large archive before copying it to removable media or a transfer system that rejects the archive as one file.
Reassembling numbered fragments received from another person after confirming that every part belongs to the same original file.

Limits and checks

Check the unit used by the part-size control. Decimal megabytes and binary mebibytes are different quantities, and another service may use the label MB differently. Leave some margin when meeting a strict external limit.
Very large sources remain subject to the browser and device's available memory, storage, and download capacity. Selecting a small part size does not guarantee that a source of arbitrary size can be processed successfully.
Do not treat the existence of a joined download as proof of integrity. A reordered or corrupted part can produce a plausible-sized but invalid result. Compare a trusted checksum of the reconstructed file when exact identity matters.

Common questions

Will each split part open as a normal file?

No. A size boundary can fall in the middle of a file header, compressed stream, media frame, text character, or other structure. The first fragment may look recognizable, but later fragments normally lack the information an application expects at the beginning of a complete file. Join all parts before judging whether the source format is valid.

Does splitting reduce the amount of data?

No. Splitting changes the number and size of files, not the quantity of source data. The payload sizes of all parts together should equal the original byte count, and joining should restore that count. Use a compression or archive tool first if the goal is to reduce transfer or storage size, then split the resulting archive if necessary.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.