What is a ARJ file?

ARJ — MS-DOS archive

What is it?

ARJ is an archive format from the MS-DOS era, built for a world where files traveled on 1.44 MB floppy disks.

Its most widely used feature was automatic multi-volume splitting: a 10 MB archive would spread itself across seven floppy disks without any manual intervention.

History & origin

Robert Jung released ARJ in 1991 — the name comes from his initials — as a rival to the then-emerging ZIP format.

It saw heavy use on file servers and in file-sharing circles of the time, before fading away along with DOS itself.

Why it is useful

A solid compression ratio for its era, paired with reliable multi-volume splitting.

It already supported recovery of damaged archives.

Limits & drawbacks

Thoroughly obsolete: no modern system opens it natively, and software still able to read it is becoming scarce.

It inherits DOS's limitations, starting with short file names.

Practical tips

If you dig up old ARJ files, convert them to ZIP right away — it's the only way to preserve their contents.

Check the result after conversion: file names truncated by DOS can come out garbled.

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