Audio

• Removed
  • Legacy audio backend (5.0) - made obsolete by Audio Mixer
  • Vivox Voice Chat (5.0) - voice chat currently supported by Audio Mixer
• Deprecated
  • Old audio system (5.x) - made obsolete by MetaSound

Core

• Removed
  • 32-bit platforms (5.x) - most supported platfroms are currently 64-bit
  • Event-Driven Loader (5.0) - replaced with Zen Loader system

Networking

• Removed
  • Legacy Socket Systems (5.0) - made obsolete by ASIO (SocketSubsystemBDS, SocketBuilders, etc.)
  • Unused Packet Encryption (5.0) - only DTLS is used currently

Non-linear animation

• Removed
  • Matinee (5.x) - deprecated for a long time, replaced by Sequencer. It's possible to convert assets.
  • Sequence Recoder (5.0) - replaced by Take Recorder.
  • Movie Scene Capture (5.0) - replaced by Movie Render Queue.

Physics

• PhysX depreacated in 5.0, replaced with Chaos.
• PhysX gonna be removed entirely in 5.1.

Programming

• Removed support for Visual Studio 2015/2017 (5.0)
• Added support for Visual Studio 2022

Rendering

• Removed
  • Legacy Tonemapper (5.0 EA)
  • Distance Field GI (5.0 EA) - replaced by Lumen
  • Light Propagation Volumes (5.0) - made obsolete by Lumen
  • Hardware Tesselation (5.0) - made obsolete by Nanite
• Deprecated
  • Cascade (5.x) - replaced by Niagara, it's possible to convert assets.
  • Atmospheric Fog - replaced by physically-correct Sky Atmosphere.

World building

• BSP (5.x) - deprecated in 5.0 EA for editing, volumes still use them. Mesh Editor Tools replace BSP for mesh editing.
• World Composition deprecated (5.0 EA), althought its code is untouched. Meant to be replaced by World Partition.

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Further read

• Upgrading to UE5 Early Access