User guide

Install

Run the setup. By default it installs for the current user only, without administrator rights, into %LOCALAPPDATA%\Programs\NikPak; its first page also offers to install for all users. It installs NikPak and unNik, adds them to the Start menu, puts NikPak on the desktop and makes unNik the program for .nik files. On request it adds the folder to the PATH for the command line.

Updates install over the previous version and keep your licence.

macOS and Linux: unpack the archive and run ./install.sh. It copies nikpak and unNik to ~/.local/bin (Linux) or /usr/local/bin (macOS) and adds the right-click menu of the file manager (Dolphin, Nemo, Nautilus; Quick Actions in the Finder). Then start the window with nikpak.

Compress with the NikPak window

1. Start NikPak. Drop files or folders on the window, or click the circle and choose Choose files or Choose a folder.
2. They are compressed with the best compression (-m5) into one archive named after the file, the folder, or the folder they came from. An existing archive is never overwritten: report.nik becomes report (2).nik.
3. The ring shows the percentage, the phase (analysing, compressing, finishing), the amount processed and the time. Cancel or Esc stops at once and removes the unfinished archive.
4. When the ring turns green: Show in folder, Open in unNik, or Compress more.

Also in the window

• Save to: the destination folder at the bottom. It is remembered; the first time it is the Desktop. The folder button next to it opens it.
• Switch to unNik: the round button left of the i button closes NikPak and opens unNik, with the new archive if you just made one.
• Language: the button at the bottom left. NikPak and unNik restart in the chosen language and share it.
• Sounds: the speaker button in the title bar switches the sound effects on and off.
• Skins: the palette button in the title bar opens the skins menu (point to try, click to keep); the sun / moon button switches between dark and bright. The choice is remembered and shared with unNik. All the skins.
• Status and About: the top left shows EVALUATION COPY · REGISTER or the licence holder; the i button shows the version and the licence.

Browse and extract with unNik

Double-click a .nik file, drop it on the unNik window or pick one of the recent archives. Encrypted archives ask for their password first. The window grows into a browser with the folder tree, the files and the details of the selected file.

• Navigate with the folder tree, the breadcrumbs, Back, Forward and Up, and double-clicks. Search finds files by name in the whole archive.
• Select with a click, Ctrl+click, Shift+click or the check boxes. Click a column title to sort. A right-click opens a menu with every action.
• Extract all or the selection: choose the destination, keep the folders or not, and what to do when a file exists: replace it, keep both or skip it.
• View text with line numbers and search, or binary files in hexadecimal. Open starts a file with its own program.
• Delete removes files from the archive after a confirmation; the archive is written again safely. Test checks every file.

Keyboard shortcuts

Register your licence

1. Buy a licence. You receive a key that starts with NPK1- by e-mail.
2. In NikPak, click EVALUATION COPY · REGISTER at the top left, or Register in the reminder.
3. Enter the name and the e-mail address exactly as on your licence, and paste the key. Case, extra spaces and the look-alike characters O/0 and I/L/1 do not matter.

Once registered, NikPak never asks again on that computer. A company can instead put a nikpak.key file next to nikpak.exe, which registers every user of that PC. From the command line:

nikpak register "Jane Doe" jane@example.com NPK1-...
nikpak license
nikpak unregister

Command line

NikPak follows the syntax RAR users know: nikpak <command> [options] <archive> [files...]. Options may come before or after the archive name; -- ends the options.

Commands

Main options

Examples

nikpak a backup.nik C:\Docs\*.txt Photos\  # create an archive
nikpak a -m5 -mt8 big.nik Projects\        # maximum level, 8 threads
nikpak a -p secret.nik Taxes2026\          # encrypted, asks for the password
nikpak x backup.nik C:\Restore\            # extract with paths
nikpak e backup.nik *.jpg C:\Pics\         # only *.jpg, without paths
nikpak x backup.nik Docs/report.pdf        # extract one file
nikpak l backup.nik *.pdf                  # list only the PDFs
nikpak t secret.nik                        # test (asks for the password)
nikpak d backup.nik Temp *.bak             # delete entries
nikpak mt song.wav tracker.mod photo.bmp   # which media filter wins?

Passwords

When an archive is created with -p, NikPak takes the password from, in this order:

• -p<password> or -P <password> on the command line (at least 8 characters);
• the environment variable NIKPAK_PASSWORD, which keeps it out of the process list;
• an interactive prompt, asked twice; an empty entry generates a random password;
• without a terminal, a password piped on the standard input, else a generated one.

Exit codes

Total Commander and other front-ends

Because NikPak accepts RAR's command syntax, a program that can drive an external rar.exe can drive nikpak.exe. In Total Commander, register the extension nik as an additional packer and point the packer and unpacker commands to nikpak.exe. Use -o+ or -y for unattended extraction. Options that RAR front-ends often send (-s, -ma5, -md64m, -ibck, -rr and similar) are accepted and ignored.

Going further

The technical guide describes the .nik format, the NAC codec, the encryption design and the complete benchmarks. Questions? Write to us.