Currently, there is a limit to the maximum count an itemstack can have in the game (99). This mod greatly increases that cap by changing the limit built into the max_stack_size data component to ~1 billion. Additionally, the default maximum stack size of most items is adjusted for a new 1000 item cap. This is also applied proportionally, so something like ender pearls (normally stacks to 16 out of the common 64 cap) will stack to 250.
Due to how significant this change is, compatibility issues may occur. Please message me or leave a comment if you encounter an issue.
Whenever you use mods, remember to make regular backups.