The short answer is of the full game released by Blizzard Entertainment. However, there are specific legal ways to access the game if you have previously owned it or if you use specific subscription services.
If you own the game or have a subscription, the installation process is handled through the Battle.net Desktop App. Warcraft III Free Download
If you still have your original Reign of Chaos and The Frozen Throne CD keys, you can link them to your Battle.net account to gain access to the "Classic" version within the modern launcher for free. The short answer is of the full game
Some fans have remade the Warcraft III experience in the StarCraft II engine (which is free-to-play). A notable project is Azeroth Reborn , which allows you to play through the original campaigns for free. How to Install Warcraft III (Official Method) If you still have your original Reign of
Log in to your Battle.net Account Overview and enter your legacy CD key in the "Redeem a Code" box.