Requires Fabric API. If you have a lot of chests nearby, you have probably noticed how bad Minecraft is at rendering them. The more chests you place, the lower your FPS go.
This mod helps by removing dynamic models from chests and making them render as static chunk geometry like normal blocks. (This means they will lose their lid opening animation!)
Depending on how many chests you have around you'll see varying effectiveness. In large storage rooms this mod can easily double your FPS. Keep in mind this mod only focuses on chests, and there might be other things crippling your FPS.
FastChest works with Sodium and Optifine and should be compatible with all other mods and resource packs that leave chests alone. One example that does not is the Vanilla Tweaks Proper Break Particles resource pack. It overwrites the chest blockstate definitions and is not compatible out of the box. You can however delete chest.json, ender_chest.json and trapped_chest.json from the /assets/minecraft/blockstates directory of your resource pack to make it work with the mod.
A classic (full-block) chest resource pack can be downloaded from here.