Achievements Optimizer Mod for Minecraft 1.20.1, 1.16.5

Achievements Optimizer is a lightweight performance mod that optimizes how item-based achievements and advancements are processed - reducing unnecessary inventory scans and improving overall tick efficiency.

It doesn’t change any gameplay mechanics or logic - only makes achievement checks faster and cleaner under the hood.

⚙️ Key Optimizations

• Early tick skipping - heavy slot calculations (empty/occupied/full) are skipped early, preventing extra work per event.
• Instant empty stack discard - with ignoreEmptyStacks enabled, empty stacks are removed immediately without scanning the entire inventory.
• Fast multi-item matching - single-pass inventory check using boolean[] flags with early exit. No allocations, noticeably faster on large inventories or long condition lists.
• Early slot filtering - slots.matches(full, empty, occupied) is evaluated first, avoiding deeper checks when slots don’t match.
• Preserved fast path for single targets - when items.size() == 1, the comparison is done directly on the changed slot without a full inventory pass.

🚀 Result

Fewer redundant checks, less memory churn, and faster responses to inventory events. Particularly beneficial for servers or modpacks with many players and complex advancement triggers.

From version 2.0.0 required Forge Config API Port (only for fabric version).

Feel free to write about all problems and suggestions on my github! Good luck!