Using Your Own PAR2, UnRAR and 7-Zip with NZB Grab

NZB Grab repairs and unpacks your downloads with tools that come built in, so there is nothing extra to install. It also lets you point it at your own copies of PAR2, WinRAR (UnRAR) and 7-Zip. So should you? For most people, no, but there are a few good reasons to.

What NZB Grab already includes

• PAR2 repair: par2cmdline-turbo, a much faster version of the standard par2cmdline that uses every core of your processor. It is the quickest PAR2 tool there is for checking and repairing downloads. Read how PAR2 repair works.
• RAR unpacking: the official UnRAR from RARLAB, the makers of WinRAR, so every kind of RAR archive is supported.
• 7z and zip: handled by a reader built into the app, with nothing to install.

The short answer: if your downloads repair and unpack fine, leave all three settings blank. You will not get faster repairs from a different PAR2 tool, because the built-in one is already the fastest.

When your own copy does help

1. Big 7z archives: install 7-Zip

The built-in 7z reader is handy, but the real 7-Zip program is faster on large .7z sets and copes with a few compression methods the built-in reader cannot. If you download a lot of 7z archives, install 7-Zip from 7-zip.org. NZB Grab finds it in its usual Program Files folder by itself, so you do not even need to change a setting.

2. A newer UnRAR before the next NZB Grab update

RARLAB occasionally releases new versions of UnRAR with support for newer archives or security fixes. NZB Grab updates its own copy with each release, but if you have WinRAR installed and want its newer UnRAR straight away, point NZB Grab at it, usually C:\Program Files\WinRAR\UnRAR.exe. NZB Grab uses its own copy over an installed WinRAR unless you set this path.

3. Antivirus or work PC rules

Some antivirus programs or work computers block helper programs that come inside other apps. If yours does, point NZB Grab at copies of the tools your PC already trusts.

4. You prefer to manage your own tools

If you already keep par2cmdline or 7-Zip up to date yourself, you can use those. It just means one more thing to keep updated.

When it will not help

• Faster repairs: no other PAR2 tool will beat the built-in par2cmdline-turbo.
• MultiPar: MultiPar’s command-line tool (par2j64) uses different commands from par2cmdline, so do not set it as the PAR2 tool. Stick with par2cmdline or par2cmdline-turbo.
• Old copies: pointing at an old UnRAR can make newer archives fail to unpack. If you set your own, keep it up to date.
• A missing PAR2 tool: if your antivirus removed it, click Re-download the PAR2 tool instead of hunting for another copy.

How to use your own tools

1. Open NZB Grab, click the cog for Settings, then Advanced.
2. Under Repair and unpack tools, click Browse next to 7-Zip, WinRAR or UnRAR, or PAR2 repair, and pick the program’s .exe file.
3. Click Save advanced.

To go back to the built-in tools, clear the box and save again. The status line above the boxes tells you which tools NZB Grab is using right now.

Where NZB Grab looks for tools

When a box is blank, NZB Grab picks a tool for you, in this order:

1. a path you have set in Advanced settings
2. a copy on your system PATH
3. the tools built into NZB Grab
4. your own drop-in folder, %USERPROFILE%\.nzbgrab\tools
5. the usual Program Files folders for WinRAR, 7-Zip and MultiPar

Because the built-in PAR2 and UnRAR come before the drop-in folder, dropping your own copies there will not replace them: set the path in Advanced instead. The drop-in folder is handy for 7-Zip, which NZB Grab does not bundle as a separate program.