The best way to experience the game (and support the developers) is to play the official version:

The game chat box appeared. It had never had a chat box before.

: Frequently hosts stable versions of the original Isaac and Wrath of the Lamb .

If you just want to play the base game quickly in a browser, look for the Classic version on sites utilizing the Ruffle emulator. If you want the full Rebirth experience with hundreds of items and modern updates, you will need to purchase the game or download it on a personal device.