In the highly anticipated release of Blender 4.0, major changes include the ability to create custom tools using Geometry Nodes, a rework of the Principled BSDF and Principled Hair BSDF shaders, light linking in the Cycles renderer, and support for Hydra rendering delegates.

The official list comprises hundreds of individual improvements, but the major and significant changes include:
Snap Base: You can now press the B key to set a base point when moving an object. This feature allows for quick and accurate snapping from a specific vertex to another.

AgX, a new color management system, is now the default setting in the update. This transformation provides improved color handling in overexposed areas compared to Filmic. Particularly, bright colors are brought closer to white, resembling real-life camera behavior.

The Principled BSDF has been reworked. Now, most parameters can be collapsed, making it more user-friendly. Changes have been made to the Sheen, Subsurface Scattering, IOR, and other parameters.

Light and Shadow Linking: These functions enable you to configure lighting and shadows to affect only specific objects in the scene.

Geometry Nodes: The release introduced the capability to specify an area that can iterate a defined node tree any number of times. Additionally, a setting was added to enable working with sharps in the nodes.

Node-Based Tools: An available way to create custom tools/add-ons without using Python. Now, node systems can be utilized as operators directly from the 3D view menu.

Modifiers: The "Add Modifier" menu has been revised and changed to a standard list-style menu, expanded with custom modifiers from geometry node group assets.
Apart from the aforementioned updates, changes have also affected rigging, pose library, bone manipulation, and many other areas.

Blender 4.0 is available for Windows 8.1 and above, macOS 10.15 and above (macOS 11.0 on Apple Silicon Mac computers), and glibc 2.28 and above for Linux. The software can be downloaded for free.