Minecraft Launcher

This is Only for Java Edition

Prism Launcher

Download - Github

PrismLauncher does not allow you to create an offline account without having a Mojang / Microsoft account.
If you click the "Add Offline" button, you will be presented with an error.
It can be easily bypassed.

1. Search for CMD and Run as administrator.
2. Then paste one of the following:

echo {"accounts": [{"entitlement": {"canPlayMinecraft": true,"ownsMinecraft": true},"type": "MSA"}],"formatVersion": 3} > %appdata%/PrismLauncher/accounts.json

3. Launch Prism Launcher, click on the top right button which displays "No profile (Xbox profile missing)" and you will notice a new offline profile has appeared.
4. Click on the Add Offline button, type in your username you want and Enjoy playing Minecraft without Mojang or Microsoft accounts, using PrismLauncher or even MultiMC and its forks.