What is a RAR file?

RAR is a container: a wrapper that holds streams encoded by something else. It is used for archiving.

The extension is .rar, and the full name is RAR Archive. Both matter less than what the file can hold, which is what the rest of this page is about.

win.rar GmbH published it in 1993.

A format that has been readable for that long is a format worth trusting with something you want back in ten years.

Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.

RAR stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.

RAR stores a directory: names, folders and the structure between them. That is what lets it stand in for a folder in an email attachment.

RAR carries a checksum, so a damaged file is detected rather than silently mis-read and optional encryption.

An encrypted file has to be unlocked before anything can convert it, here or anywhere else — a password is not something a converter can work around, and one that claimed to could not be trusted with the file either.

WinRAR, 7-Zip and Keka read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

RAR is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.

The recurring complaints: support outside its home ground is uneven.

None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.

RAR is not a format people pick for themselves any more. It arrives: from a download, from a colleague running WinRAR because it came with the machine, from an archive assembled a decade ago, or from a forum where the convention was set long before anyone questioned it.

So the question is almost always how to open one rather than whether to use one. That is worth naming up front because the two halves of RAR are not equally available — reading one is straightforward, and creating one is a licensing matter rather than a technical one.

RAR was created by Eugene Roshal in 1993 and the compression algorithm remains proprietary. The decompression side has been published and can be implemented freely, which is why so many tools open RAR files. The compression side has not, and writing one legally means licensing it from the owner.

That asymmetry explains almost the whole landscape. Every archive utility can extract a RAR; only WinRAR and a handful of licensees can produce one. It is also why Quinvert extracts RAR and does not create it — not a missing feature, a licence we do not hold and would not be able to satisfy in a static site.

RAR generally beats ZIP, and the gap is real rather than marketing. On mixed documents expect something in the region of ten to twenty per cent smaller; on large collections of similar files the advantage widens considerably, because RAR can treat the whole set as one stream and find repetition across file boundaries.

ZIP compresses each file independently, which is what makes it fast to extract one item from a large archive and what costs it size on a thousand near-identical files. Neither behaviour is wrong. It is a trade between random access and ratio, and RAR chose ratio.

RAR splits an archive across numbered volumes — `.part1.rar`, `.part2.rar`, and so on, or the older `.r00`, `.r01` scheme. The convention comes from the era of floppy disks and upload limits and survives wherever a single file would be too large for the channel.

They are not independent archives. Every part must be present in the same folder before extraction can begin, and opening part one is how you extract the whole set, not the first third of it. A missing middle part usually means everything after it is unrecoverable — which is the most common reason a RAR extraction fails partway with no obvious explanation.

RAR can store redundant data inside the archive specifically so that a damaged file can repair itself. If a few bytes are corrupted in transit or on a failing disk, an archive with a recovery record can often reconstruct them without the original.

ZIP has nothing equivalent, and this is the one feature that still earns RAR a place. It is why archives meant to sit on optical media, survive unreliable transfers, or be stored for years were often made as RAR by people who had thought about it rather than by habit.

RAR supports AES encryption of the file contents, and unlike ZIP’s original scheme it is properly implemented. A password-protected RAR is not trivially broken; without the password the contents are genuinely unavailable.

By default the list of file names remains readable even when the contents are not, so an observer can see what the archive holds without opening it. WinRAR has an option to encrypt the names as well, and it is off unless someone chose it. If the file names themselves are the sensitive part, that distinction matters.

The format changed substantially with WinRAR 5 in 2013 — new compression, larger dictionaries, a different structure. Archives written in the new format are not readable by tools that only understand the old one, and there is no way to tell from the extension.

A tool from before 2013, or one whose RAR support was never updated, will report an unknown or corrupt archive on a perfectly intact file. If a RAR refuses to open in one program and works in another, this is the usual explanation, and updating the extractor is the fix rather than repairing the file.

For anything that has to be sent onward, repackage as ZIP. Every operating system in current use opens ZIP without installing anything, which RAR cannot claim — a recipient on a stock Windows or macOS machine may have no way to open a RAR at all, and sending one is quietly asking them to install software.

For something being kept rather than sent, leaving it as RAR is fine and there is nothing to gain from converting. Repacking recompresses everything for no benefit, and if the original carries a recovery record, converting throws away the one thing RAR does that nothing else does.

The contents of an archive are the contents of an archive: tax documents, photographs, source code, scanned paperwork, a backup of somebody’s entire home directory. Handing all of that to a website in exchange for a download link is a poor trade that people make routinely because there is no obvious alternative.

RAR is the family where this site cannot offer one. Nothing that runs in the browser reads the format, so a RAR dropped here goes over an encrypted connection to the conversion API and is unpacked inside a container that has no internet access of its own: unrar-free reads the archive, because the Debian build of 7-Zip ships without the RAR codec, and 7-Zip writes the ZIP, 7z or TAR you asked for. The job directory is deleted when the job ends, whether it succeeded or not.

That route carries two limits the browser pairs do not. A server file is capped at 25 MB rather than the 100 MB that applies on your own machine, and server conversions spend an allowance of a hundred a day, counted against a salted daily hash of your address rather than an account, and reset at UTC midnight rather than carried over. For a multi-gigabyte archive, or for contents that should not travel at all, 7-Zip and WinRAR do the same extraction on the desktop and nothing leaves the machine.