Also on curseforge

Forge mod.

Uninstalling older versions of this mod
and using it on a world that previously had it installed may have
negative consequences!

Bigger stacks

Allows you to increase stack size beyond
64, up to ~1 billion (though I don't recommend you go that high).

Control the stack size of individual items

The mod allows you to change the stack
size of items based on tags, what mod it comes from, and more using
rules.

Quickstart

When you load into a world with the mod
unconfigured, it will show you this prompt:

Clicking on the command or running it
will open a configuration GUI.

You can open this GUI at any time by running /biggerstacks quicksetup

Compatibility

With a mod like this, it is very likely
that some things will be incompatible. If you find any issues, or things
not working as expected, report them on codeberg.

Some item transport mod (xnet, modular
routers, pretty pipes, cyclic) have been changed for bigger stacks.
There is some more information about the changes in the config
file.

Please
report any issues/incompatibilities you find with this mod to me, not
the author of the other mod.

1.12?

There are very similar mods for 1.12 already available