Statistics track time spend doing something, distance traveled or jumped, and how often the player interacted with blocks or performed certain actions.

To add a custom statistic, create an identifier which will be used to register and increase the stat:

public static final Identifier INTERACT_WITH_COOL_BLOCK = new Identifier("modid", "interact_with_cool_block");

Then register the stat using the identifier:

Registry.register(Registry.CUSTOM_STAT, "interact_with_cool_block", INTERACT_WITH_COOL_BLOCK);

Then add the stat to the statistic screen, where you can also specify the stat formatter. It determines how the number is shown in the stat list. You can use DEFAULT, DIVIDE_BY_TEN, DISTANCE or TIME.

Stats.CUSTOM.getOrCreateStat(INTERACT_WITH_COOL_BLOCK, StatFormatter.DEFAULT);

To increment the statistic, for example when a player interacts with a block, you can use PlayerEntity::incrementStat:

@Override
public ActionResult onUse(BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockHitResult hit) {
	player.incrementStat(ModClass.INTERACT_WITH_COOL_BLOCK);
 
	return ActionResult.SUCCESS;
}

You can also use PlayerEntity.increaseStat(stat, amount) to increase the stat by an arbitrary amount.

To translate the name, add an entry for stat.modid.statid (see lang for how to translate the statistic.):

{
  "stat.modid.interact_with_cool_block": "Interactions with Cool Block"
}