The term "portable" in this context usually refers to a standalone version of the DLL that can be "dropped in" to a game's installation folder.
The Invisible Upgrade: Mastering ffx_fsr2_api_vk_x64.dll for Portable Vulkan Gaming ffx fsr2 api vk x64dll portable
In the modding community, the FSR 2 API DLL is often utilized as an injection agent. Modders may utilize the dxgi.dll or vulkan-1.dll proxying technique to force games without native upscaling support to load the FSR 2 logic. In these scenarios, ffx_fsr2_api_vk_x64.dll is loaded as a dependency to handle the heavy lifting of temporal upscaling, effectively "porting" the technology to legacy titles. The term "portable" in this context usually refers