Upgrade hoppers to transfer items between two chests automatically (mainly for Automate users).

Install

Install the latest version of SMAPI.
Unzip the mod folder into Stardew Valley/Mods.
Run the game using SMAPI.

Use
For players
Left click a Hopper with an iridium bar, and it will change colors and start moving things from a chest immediately above it to one immediately below it. Left click with an empty hand to downgrade it and get your iridium bar back.

For example, you can use this to create automated supply chains. Note how Automate sees three separate machine groups, so the shipping bins in the third group can't steal milk from the chest in the first group:

Compatibility
Compatible with Stardew Valley 1.5.5+ on Linux/macOS/Windows, both single-player and multiplayer.

See also

Super Hopper