This update is out now for all platforms.
A man and a young woman, both with silver hair, are sitting on grass and leaning back against a large tree. They are both wearing medieval-era looking clothing and armor. The man has two swords on  his back and has a well trimmed beard. Both of them have a scar over their left eye.

The 4.01 update for The Witcher 3: Wild Hunt came out today for PC, PlayStation, and Xbox. There are a few PC-specific improvements, a few console-specific improvements, and some general fixes for all platforms. Minus a couple of hotfix updates, this is the first major update to the game since the next-gen version of The Witcher 3 was released in December.

Patch 4.01 includes a new performance mode for ray-traced global illumination on PC. There is also a fix for screen space reflections on PC. Apparently they weren't working before. I honestly don't think I even noticed that when I played through the game a couple of weeks back. Console players will see improved screen space reflections, optimized ray-traced global illumination, and enjoy a fix for there being too many save slots.

Just from a quick glance of the CD Projekt Red forums, users noted that this update also offers players the option to toggle vignette on or off on consoles, along with a toggle for chromatic aberration.

The full changelog for Patch 4.01 is below via TheWitcher.com.

PC-SPECIFIC
  • Fixed an issue where the Screen Space Reflections setting wasn't working on PC despite being turned on. Players who had previously set their SSR setting to high may notice a performance impact.
  • Added a new performance mode for ray-traced global illumination, which can be toggled by players with compatible hardware. It improves frame rate by prioritizing performance over range and precision.

CONSOLE-SPECIFIC
  • Fixed an issue where consoles could create a higher amount of saves than their set limit, resulting in various issues with saving the game or user settings being reset.
  • Improved Screen Space Reflections quality on next-gen consoles.
  • Optimized ray-traced global illumination on next-gen consoles to improve the performance of Ray Tracing Mode.

QUESTS & GAMEPLAY - Available on all platforms
  • Battle Preparations - Fixed an issue where it could be impossible to interact with Avallac'h during the objective "Let Avallac'h know everything's ready."
  • Family Matters - Fixed an issue that could cause the game to crash during the transition to Ciri's Story: Out of the Shadows when speaking to the Bloody Baron.
  • King's Gambit - Fixed an issue where it could be impossible to participate in the fistfight with the second Vildkaarl due to an invisible obstacle.
  • Wine Wars: Belgaard - Added a retrofix for the issue we fixed in 4.00, where the quest couldn't be completed if the player destroyed one of the required monster nests during exploration.
  • A Dangerous Game - The armor in Caesar's room should now change its appearance when the Alternate Nilfgaardian Armor is turned on.
  • Axii Puppet - Increased the health and damage dealt by the puppet.
  • Adrenaline Rush mutation should now work according to its description.
  • Various small fixes to quests and cutscenes.

LOCALIZATION - Available on all platforms
  • Fixed various issues with Arabic localization.
  • Added the localized versions of Orianna's song "Lullaby of Woe" in Korean and Simplified Chinese.
  • Adjusted Priscilla's lip-sync animation to match her voice-over in Simplified Chinese during the song "The Wolven Storm".
Please note: these are only the most notable changes. The patch contains other minor fixes that didn't make it into this list.​