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 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. Warcraft III Free Download
Log in to your Battle.net Account Overview and enter your legacy CD key in the "Redeem a Code" box. Some fans have remade the Warcraft III experience
Download and install the Battle.net App. Warcraft III Free Download