Darts 501 is the format the professional game is built on. Both players start on 501 and subtract whatever they score, and the winner is the first to reach exactly zero. Overshoot and the whole turn is void, which is why the last hundred points are where matches are actually decided.
The arithmetic is the hidden half of the sport. Good players are not just accurate, they know instantly which number to hit to leave themselves a finish, and they think two turns ahead about the total they want to be on. Scoring big is easy; setting up a checkout is the skill.
Tips & strategy
Aim at the treble twenty while your score is high. Sixty a dart is the fastest way down from 501, and the early part of a leg is purely about scoring heavily rather than precision on specific numbers.
Switch to setting up a finish below about 170. From that point the goal is not the biggest score but landing on a number you can actually check out from, ideally an even total that leaves a double.
Learn a few common checkouts. Knowing that 40 is double twenty and that 32 leaves double sixteen, which halves neatly if you miss, saves you from stumbling around awkward odd numbers at the end of a leg.
Avoid leaving odd totals. An odd number cannot be finished on a double, so you have to waste a dart correcting it. Planning to leave an even number is the single most useful habit in 501.
Questions
Why does going below zero not count?
Finishing requires landing on exactly zero. Overshooting is a bust and the whole turn is void, with your score returned to where it started.
What is a checkout?
The sequence of throws that takes you from your current score to exactly zero.
Why is 32 a good number to leave?
Because it is double sixteen, and missing into a single leaves 16, which is double eight, and so on. It halves cleanly.
Can I play a friend?
Yes, taking turns on the same device.
Is there anything to install?
Nothing at all. The whole of Darts 501 is built into the page itself, which is why there is no loading bar and no waiting before you can play.