- Legacy audio backend (5.0) - deprecated, made obsolete by Audio Mixer
- Old audio system (5.x) - made obsolete by MetaSound
- 32-bit platforms (5.x) - most supported platfroms are currently 64-bit
- Event-Driven Loader (5.0) - replaced with Zen Loader system
- Legacy Socket Systems (5.0) - made obsolete by ASIO (SocketSubsystemBDS, SocketBuilders, etc.)
- Unused Packet Encryption (5.0) - only DTLS is used currently
- 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.
- PhysX depreacated in 5.0, replaced with Chaos.
- PhysX gonna be removed entirely in 5.1.
- Removed support for Visual Studio 2015/2017 (5.0)
- Added support for Visual Studio 2022
- 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
- Cascade (5.x) - replaced by Niagara, it's possible to convert assets.
- Atmospheric Fog - replaced by physically-correct Sky Atmosphere.
- 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.