Recs.
Updated
Specs
Pros
Cons
Con The homepage is not good
The homepage allows players to join your game, but the way it works is just not good. The "unpopular 0 player" games get less exposure than the popular games. The tier system also puts a star on your game card which also lures players to your game making them think this game has a special event or something, giving a disadvantage to the less popular games which are still so called "Tier 1".
Con Limited customizability
Modd.io is designed to be good at making "specific" kind of multiplayer games. Its strength unleashes if you don't care too much about the specifics in UI. For example, if you wanted to make a casual death match game, it is extremely easy to make it using modd.io. However, if you want to create a puzzle game with a unique UI, it becomes very time consuming.