Hopper Lock Visualizer
by Scainest
Hopper Lock Visualizer lets a player see at a glance which hoppers are locked by a redstone signal, drawing a red outline around each one.
What it does
Hoppers stop moving items when they receive a redstone signal, and the cause is often a stray wire, a comparator or a torch nearby. The mod scans the area around the player and marks every locked hopper with a red wireframe, so a broken item sorter can be traced to the hopper that is blocked. A single key toggles the overlay, and the default key is H, which can be rebound in the Controls options.
The scan covers a 32-block radius around the player and refreshes twice per second. Only hoppers within the view cone are drawn, and distant ones are culled, so a large base with hundreds of hoppers adds little cost. The overlay uses the Gizmo API introduced in Minecraft 1.21.11. The mod is client-only, so no server installation is needed, and it works with zero configuration after installation. Files are published for Fabric only, for 1.21.11, with 1.0.0 dated 2026-04-14 as the latest file.
Key features
Locked hopper outlines
Hoppers that have lost their ability to pass items are outlined in red, so the blocked one is simple to spot.
One-key toggle
Pressing H turns the overlay on or off, and the key can be changed in the Controls options.
Scan around the player
Hoppers within a 32-block radius are checked twice per second, so the display follows the player as they move.
View-based culling
Distance and view cone checks limit drawing to hoppers the player can actually see.
Gallery
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Finding a broken item sorter
When a sorting line stops, the outline shows which hopper is receiving a redstone signal it should not have.
Large redstone bases
The scan handles many hoppers at once, so the overlay stays useful in sprawling contraptions.
Who it’s for: Players building item sorters and automated storage on Fabric for 1.21.11 who want to find hoppers blocked by unintended redstone signals.
How it compares
Wireframe is a Fabric client-side mod for 1.21.1 under the MIT License, but it is not open source. Simple Tools is open source under the CC0 1.0 Universal license and runs on client and server for 1.21 – 1.21.1. Wireframed is client-side only for 1.21.11 under All rights reserved, with no open-source code.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Hopper Lock Visualizer | Fabric | 1.21.11 | Client-side only | 2026-04-14 |
| Wireframe | Fabric | 1.21.1 | Client-side only | 2025-01-20 |
| Simple Tools | Fabric | 1.21 – 1.21.1 | Client and server | 2025-08-21 |
| Wireframed | Fabric | 1.21.11 | Client-side only | 2026-02-13 |
Questions
Does Hopper Lock Visualizer need to be installed on the server?
Which Minecraft version does the mod support?
Can the H key be changed?
In the catalog
Hopper Lock Visualizer is one of 36,990 Utility mods on ModsFinder, and one of 25,772 Utility mods for Fabric. 19,862 mods support Minecraft 1.21.11.
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What the author says
Built an item sorter and something isn't working? One of your hoppers is probably receiving an unintended redstone signal. This client-side mod wraps every locked hopper near you in a bright red outline, so you can spot the culprit at a glance. When a big contraption stops working, 9 times out of 10 the cause is a…
Official listing
- Modrinth page
- modrinth.com/mod/hopper-lock-visualizer
- Owner
- Scainest
- Published
- 2026-04-14
- Updated on Modrinth
- 2026-04-14
- Facts verified
- 2026-10-15