Download modern clients like vkQuake or ezQuake.
You can legally obtain verified PAK files in three ways:
Many sites offer the "shareware" PAK file for free. The shareware PAK only includes the first registered level set (Episode 1). If you need the full game (Episodes 2-4), downloading an unverified "full PAK" from a random blog violates copyright. The only legal way to get the full PAK files is to own the game.
Finding a verified, legal, and safe download for Quake 1 PAK files can be confusing due to decades of community files and sketchy abandonware sites. This guide covers how to get verified Quake PAK files legally, how to verify their integrity, and how to install them. What Are Quake 1 PAK Files?
Technically, a PAK file is a raw file system archive. It contains a header identifying the file and an offset to the file allocation table (the "directory"). This directory tells the engine where specific files (like progs.dat for game logic or start.bsp for maps) are located within the binary blob.
If you simply want to experience the classic gameplay without purchasing the game, the is legally distributable.