Free to Play:
* Pokemon Showdown: This is a turn-based battling simulator where you can create teams, battle other players, and explore various metagames. It's a great way to practice your strategy and learn about different Pokemon. [https://pokemonshowdown.com/](https://pokemonshowdown.com/)
* Pokemon Uranium: This is a fan-made Pokemon game that is incredibly popular. It features new Pokemon, regions, and gameplay mechanics. However, it is a downloadable game, not an online one.
* Pokemon Insurgence: Another fan-made Pokemon game with a unique storyline and gameplay. It's also a downloadable game.
* Pokemon World Online: This is a browser-based MMORPG where you can explore a world, catch Pokemon, battle other players, and trade Pokemon. It's not as polished as the main series games, but it's a fun experience for free. [https://www.pokemonworldonline.net/](https://www.pokemonworldonline.net/)
Subscription-based:
* Pokemon GO: This is a mobile game that uses Augmented Reality to bring Pokemon into the real world. While it's not like the main series games, it's very popular and offers a unique experience.
* Pokemon UNITE: This is a mobile and Switch game that is a MOBA (Multiplayer Online Battle Arena) based on the Pokemon franchise.
Other Options:
* Emulators: You can download emulators for older Pokemon games and play them on your computer. You can find ROMs (game files) online, but it's important to ensure you're only downloading from reputable sources.
* Fan-made Games: There are many fan-made Pokemon games out there, including ROM hacks, fangames, and browser-based games. You can find them on various websites like Pokemon Fan Games and Game Jolt.
Keep in mind:
* Legality: Most online Pokemon games are not officially authorized by Nintendo. Be careful about downloading or playing games from unofficial sources.
* Quality: The quality of online Pokemon games can vary greatly. Some are well-made, while others are more basic.
* Gameplay: Online games can be different from the main series games in terms of gameplay, mechanics, and features.
Ultimately, the best option for you will depend on your preferences and what you're looking for in a Pokemon experience.