Playing Battlefield 3 Online Without the Disc: Is It Possible?

No. The Xbox 360 / PS3 versions of Battlefield 3 require the multiplayer disc (Disc 2) in the drive to access online modes. The disc contains the MP executable and license verification.

Why Disc Is Mandatory

• Disc-based DRM: Game checks for physical media on launch
• No "Play Anywhere" / digital license transfer for this title on last-gen

Legal Alternatives

• Buy Digital: Purchase Battlefield 3 on Origin (PC), Xbox Store (Backwards Compat on Xbox One/Series), or PS Store (PS3 only — PS4/5 cannot buy PS3 games directly). Digital versions don't need a disc
• Game Share: On Xbox One/Series, set a friend's console as your Home Xbox to share your digital license

What Doesn't Work

• ISO loading / JTAG / RGH — bans, instability
• Disc drive emulators (Xkey, etc.) — detectable, bans

Support the developers; grab the digital version on sale (often <$10).