A 1.8.9 client, and nothing else.
Quasar is a standalone Minecraft 1.8.9 client built around two things: what latency actually feels like to play on, and getting frames back by not drawing what you cannot see.
Not a mod you install
Quasar is not a Forge or Fabric mod. It modifies Minecraft's own classes at load time through SpongePowered Mixin, with its own launch path, which is why it can work inside the networking and rendering layers rather than around them.
There is no Forge and no FML anywhere in it. The launcher installs the client on first run, handles sign-in, and updates itself after that. Windows, built on JDK 8.
Why 1.8.9 only
1.8.9 is still where competitive Minecraft PvP lives, and it is a fixed target: the combat model does not move under you, so work done on hit registration and prediction keeps being worth something.
Supporting five versions badly is easy. This is one version, done properly. Others are possible later, and are not promised now.
What is in it
23 modules today. The latency and prediction work is the part that justifies the project; the rest is the HUD, visual and quality-of-life set you would expect from a client in this space, including a full HUD editor with snapping.
Everything is a toggle, everything is off unless you turn it on, and the settings are stored per server if you want them to be.
What it will not claim
It will not claim to lower your ping, because it cannot. Every performance-adjacent feature in the client carries that caveat in its own description, and the site is held to the same line.
There are no invented benchmark numbers here either. When there are published measurements, they will come with the hardware, the server, the sample size and the date, or they are not worth reading.
Who makes it
Quasar is built and published by WrenchyProductions. It is free, and it is not open source.
Bugs, requests and arguments about hit registration are welcome in the Discord.