1. HBO Max: Friends is currently streaming on HBO Max in the United States. All ten seasons, including Season 4, are available to stream with a subscription.
2. Amazon Prime Video: Friends is available as a purchase option on Amazon Prime Video. You can buy individual episodes or the entire season of Season 4.
3. Google Play: Similar to Amazon Prime Video, Friends is available for purchase on Google Play. You can buy individual episodes or the complete Season 4.
4. iTunes: Friends can also be purchased and streamed on iTunes. Individual episodes and the entire Season 4 are available for purchase.
5. DVD or Blu-ray: If you prefer physical media, you can purchase the Friends Season 4 DVD or Blu-ray set. This allows you to own the episodes and watch them offline.
Please note that the availability of Friends on these platforms may vary based on your geographical location. It's recommended to check the respective platforms for your specific region to confirm availability.