- MTG Arena if you want a Hearthstone-like experience (free, great animations/sounds, but microtransactions or grinding to stay competitive)
- untap.in or Tabletop Simulator for completely free, though a rules engine doesn't exist so you'll need to know the rules properly yourself
- MTG Online which includes a rules engine but you'll need to pay for cards
- XMage which is free and includes a rules engine, but the UX is the worst of the above
I play mostly Arena, with a bit of untap when I want to play Commander/EDH.
- MTG Arena if you want a Hearthstone-like experience (free, great animations/sounds, but microtransactions or grinding to stay competitive)
- untap.in or Tabletop Simulator for completely free, though a rules engine doesn't exist so you'll need to know the rules properly yourself
- MTG Online which includes a rules engine but you'll need to pay for cards
- XMage which is free and includes a rules engine, but the UX is the worst of the above
I play mostly Arena, with a bit of untap when I want to play Commander/EDH.