Spawner Insight

Spawner Insight

Look at a spawner. See exactly why it isn't working.

Built a mob farm around a dungeon spawner and nothing comes out? Spawner Insight shows a small panel next to your crosshair whenever you look at a spawner. It tells you whether the spawner is ACTIVE or BLOCKED, and why, in plain words.

What it checks

Spawner Insight checks the same things the game checks every time the spawner tries to spawn a mob:

| Check | Example message |
|---|---|
| Player range | Player too far: 23.4 / 16 blocks |
| Empty spawner | No entity configured (empty spawner) |
| Difficulty | Peaceful difficulty: no monsters spawn |
| Mob cap around the spawner | Too many mobs nearby: 6 / 6 max |
| Room for the mob's hitbox | Not enough room on 114 of 147 spots (mob is 4 × 4 blocks) |
| Block light (torches, lanterns…) | Too much block light (torches…) on 36 of 147 spots (light 14, max 0) |
| Sky light (daytime) | Too much sky light on 97 of 147 spots (light 15, max 7) |
| Too dark (animals) | Too dark on 49 of 147 spots (light 4, min 9) |
| Ground | Wrong ground on 97 of 147 spots (needs: Mycelium) |
| Forbidden ground | Forbidden ground on 49 of 147 spots (no Nether Wart Block below) |
| Height | Wrong height on 97 of 147 spots (only layers 50 to 63) |
| Water / liquids*| Not enough water on 97 of 147 spots |
| Entities in the way | An entity is in the way on 3 of 147 spots |
| Players too close (silverfish, endermites) | A survival player is too close… (must be over 5 blocks away) |

When the spawner works, the panel shows how many spots are valid and roughly when the next attempt happens. It also adds mob-specific tips, such as "Ghast: only a 1 in 20 chance per spot on each attempt".

What "147 spots" means

A spawner picks random spots in a 7 × 3 × 7 area around itself (with the default spawn range of 4). Spawner Insight tests every one of these 147 spots, so you can see whether the whole area is blocked or only part of it.

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 Accurate for every vanilla mob

Spawner Insight doesn't guess. It runs Minecraft's own spawn rules on every spot: the same code a spawner uses, including each mob's special conditions. Mooshrooms need mycelium. Fish and squid only spawn between layers 50 and 63. Monster spawners in the Overworld need block light 0, so a single torch nearby is enough to stop a skeleton spawner.

Every vanilla mob (79 of them) is checked by automated in-game tests in several setups (dark room, grass at noon, grass at midnight, flooded room).

A few honest limits:

- Slimes depend on the world seed (slime chunks), which the client doesn't know. Below layer 40 the panel says so instead of guessing.
- Modded mobs are checked with their real spawn rules when possible. If a rule can only run on the server, the panel marks those spots as "Cannot be checked client-side" rather than inventing an answer.
- Some mobs have random spawn rules (for example the Ghast's 1 in 20). A spot is "valid" when a mob can spawn there, even if it doesn't do so every time.

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Client-side only

- Install it on your client. It works in singleplayer and on any server, even one without the mod.
- It only reads what the server already sends to your game. It doesn't add blocks, items or commands, and it never changes the world.
- It doesn't overlap the top-center tooltip used by Jade / WTHIT. The panel sits next to your crosshair and follows your head with a slight sway.

Compatibility

- Minecraft 1.20.1
- Fabric (requires [Fabric API](https://www.curseforge.com/minecraft/mc-mods/fabric-api)) or Forge 47+
- Java 17 or newer
- Languages: English, French

License

MIT. Feel free to include it in modpacks.