A client-side Minecraft 1.12.2 mod that lets you select mobs to view spawn conditions and track live, no item required.

Features

GUI accessible via keybinding (default O) or Inventory button.
Filterable scrolling list of mobs on the left; right panel shows details and spawn conditions.
Live tracking on the main screen for selected mob. Double-click a mob in the list to toggle tracking.
Click on the biomes list to copy biome names to clipboard.
Configs:
- enableTracking: Globally disable tracking (requires restart).
- detectionRange: Set radius for considering spawn attempts.
- spawnCheckRetries: Set maximum retries for spawn condition checks. Higher values handle random spawn conditions better but increase analysis time on selection. This can lead to some high delays when selecting some mobs with tricky spawn conditions.

Q&A

Do I need to install this on a server?

No, this mod is client-side.

Is it fine to put in on server-side either way?

It is fine, the mod will simply not do anything server-side.

How is the mobs list filtered?

The filter box matches both localized and unlocalized mob names. This means you can type the mod name, the name in your selected language, or the default English name.

The spawn conditions seem off, why?

Many mobs have inherently random spawn conditions that may not be fully captured by the analysis. Increasing the spawnCheckRetries config can help, but the conditions could still be sparse. Refreshing the selection may also yield different results due to this. This is also why some mobs can be slow to analyze (taking a second).

Some biomes/dimensions/blocks show up as raw registry names, why?

Some mods do not provide proper localization keys for their biomes/dimensions//blocks. In this case, your modpack should provide a lang file with the appropriate keys to get proper names. Considering a raw name of <modid>:<biome_name>, the localization key format is biome.<modid>.<biome_name>.path for biomes, dimension.<modid>.<dimension_name>.path for dimensions, and tile.<modid>.<block_name>.name for blocks. I will not include other-mods-specific localization in the mod itself. Of course, if localization for these exist, it is a bug and should be reported.

Curseforge icon by Star Artsy.