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TAR
What is a TAR file?
Bundles files without compressing them. The Unix packaging step, usually paired with GZ.
What TAR is
TAR is a container: a wrapper that holds streams encoded by something else. It is used for archiving and moving data between programs.
The extension is .tar, and the full name is Tape Archive. Both matter less than what the file can hold, which is what the rest of this page is about.
Where TAR came from
It dates from 1979. The specification is POSIX.1-2001 ustar.
A format that has been readable for that long is a format worth trusting with something you want back in ten years.
The specification is public
Anyone can implement it without asking permission or paying a licence, which is why it turns up in so many programs and why files written twenty years ago still open.
Nothing is thrown away
TAR 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.
It can hold a whole folder
TAR stores a directory: names, folders and the structure between them. That is what lets it stand in for a folder in an email attachment.
What it does to protect itself
TAR carries a checksum, so a damaged file is detected rather than silently mis-read.
A checksum will not repair anything. It tells you the file is wrong, which is the difference between finding out now and finding out from whoever you sent it to.
What opens TAR
tar, 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.
Opening it in a browser
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.
It is a working format
TAR is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.
What goes wrong with it
The recurring complaints: the files are large for what they contain.
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.
The facts, in one place
| Extension | .tar |
|---|---|
| Media type | application/x-tar |
| First published | 1979 |
| Specification | POSIX.1-2001 ustar |