If you search for "BTD5," you will likely end up on the official Ninja Kiwi site or Steam, which are usually the first sites blocked. Here are the best places to look for the unblocked version:
Since Adobe Flash is no longer supported, many unblocked versions of BTD5 are converted to HTML5. This is actually better for you—it means the game runs smoother, doesn't crash, and saves your progress locally on the browser. btd5 unblocked games
But then, you type it into the search bar: If you search for "BTD5," you will likely