What is a PAR

What is a PAR file? (and how to use them)

A PAR file is a parity file.  PAR files typically have the extension .PAR or .PAR2 (or .p01, .p02, etc.).

PAR files are sometimes referred to as “Parchive” files.  These parity files (or par files for short) create redundant data that can be used later in case parts of the original data are lost or become corrupted.

PAR files allow for the file level recovery of data.  So, out of a group of many files (such as RAR archives), if a limited number of files are lost or corrupted, they can be recovered.  PAR files enable the recovery.

Think of PAR files like little versions of “Mr. Fix It”.  They fix RAR files that are broken.

PAR files on Usenet

PAR files on Usenet are very common.  Typically when someone uploads a volume of RAR archives, they will also include PAR files.

The person includes PAR files with the RAR volumes because as data is transferred amongst Usenet servers, and between newsgroups, the RAR files can become corrupted, lost, or damaged.  This is especially true when dealing with large RAR archives, where there may be upwards of 90 or more RAR files (.ro1, .r02, .r99, etc.).  In general, if you intend on uploading a volume of RAR files to Usenet you should include PAR files.

The PAR files will allow anyone who downloads the volume of RAR files to rebuild any (or all) of the corrupted files.  This is why PAR files are called “parity” files.

How to Open and Use PAR Files

Download and install QuickPAR.  QuickPAR is a free program.  QuickPAR will enable you to open the PAR files and check the integrity of the RAR files.

Once you have installed QuickPAR, and you open a PAR file, a check will begin on the RAR archives that the PAR file is associated with.  PAR files are always associated with particular RAR files, since the PAR files carries parity data for the RAR files, allowing them to be rebuilt if needed.

You can open any PAR or PAR2 (or SFV) files with QuickPAR.  They will have the extensions of .par, .p01, .p02 etc.

Once the check is complete, QuickPAR will alert you if a rebuild/recovery needs to be completed.  If a rebuild/recovery is needed, QuickPAR will tell you if enough “parity blocks” exist to complete the rebuild/recovery.  Each PAR file carries the parity blocks.  The bigger the PAR files (in size), the more parity blocks they contain.  If you have enough blocks, you can begin a rebuild/recovery.  Simply click the button in QuickPAR and sit back and watch the magic of “parity”!