Modern OptiFine alternative.

Additive is a simple, modern, open-source alternative to OptiFine for the most recent versions of Minecraft. It has basically every feature from OptiFine, including:

• Major FPS and logic performance improvements
• Built-in shader pack support
• Extra resource pack features, e.g. CIT
• Camera zoom to see further
• Dynamic lighting with items
• Better grass and snow
• OptiFine donator capes (and free capes)
• Other features listed here

There are also these extra features included:

• Free, simple world hosting
  • Simply click "Open Externally" in the menu of your world and you'll get a shareable IP
• Modularity
  • Lets you disable features that are incompatible with other mods or features you dislike
• Fast updates
• Other features listed here

For more information, read through Additive's Modrinth page.

How do I get it?

For installation and downloads, see this page. It provides instructions for third-party launchers and also an installer for the Mojang launcher.