Smart Vector Table
Noodlemire

API that adds a way to create tables indexed by 3D Vectors.

Multiblock Lib
Mindcool25

Multiblock structure handler

item_monoids
fluxionary

an API for controlling item properties via monoids

more_player_monoids
fluxionary

more player monoids

Wield Gadgets
1F616EMO

Register gadgets that can be used with a hotkey

Minebase Core
ThatCommand

Adds APIs and new dynamic functionalities.

Timekeeper
sorcerykid

Timekeeper acts as a centralized dispatcher for all time-sensitive routines

Random Messages
1F616EMO

Register random announcements

Telegram
neko259

Integration with telegram messenger chat

GroupLib
rudzik8

General grouping API

toolcap_monoids
fluxionary

an API to allow multiple sources to apply changes to a tools's capabilities.

DataMiner
sorcerykid

DataMiner is an analytical tool for server operators with a feature-rich API for customized report generation

verbana
fluxionary

verification and banning

DeltaTime
SkyBuilder1717

Adds deltatime API

status effects
fluxionary

api for defining player status effects

YALib
hutzdog

Yet Another Library

name monoid
fluxionary

flexible control of a player's nametag

Stent
AFCM

A formspec based arena entrance type for arena_lib

BigNum
ThePython10110

A library that adds a data type for arbitrary precision integers

Level API
Hypernoot

A library for games to load levels defined as schematics

SSCSM implementation
Luke

A server-sent CSM library.

More vector helpers
Hybrid Dog

Adds more vector functions.

Extended Protection
1F616EMO

Extended interaction restriction rule

node entity queue
fluxionary

a queue for spreading out the generation of node entities over multiple server steps (smartshops, signs, itemframes, etc).

SmartFS
rubenwardy

A library to allow mods to make Formspecs, a form of GUI, easily.

Minetest Systemd (API)
Piezo_

Debugging utility and compatibility tools for server owners and/or modpack creators

Minetest HTTP API QoS control queue
SX

Improve quality of important HTTP requests by grouping requests into service quality buckets.

Timed World Modifiers library
karamel

Environmental ABM that could be triggered on a very wide range of nodes but only a few at a time.

Debugging Console
sorcerykid

Provides an in-game HUD to easily monitor debug output

rcsv
Wuzzy

RFC-4180-compliant CSV parser and writer

Natural Entities
nurd3

A lightweight API for spawning random entities

description_monoids
fluxionary

API to allow multiple mods to make modifications to an itemstack's description

MFSM Multiple Finite State Machine
Sumi

Allows for multple states to be active, while maintaining typical state machine behavior. Good for gamestate and mobs.

YL Scheduler
AliasAlreadyTaken

Execute tasks based on utc

Gettime
1F616EMO

A api to get in-game hour/minute

YL Ticker
AliasAlreadyTaken

Displays messages once per timeframe

Bitwise Operations
sorcerykid

A pure-Lua implementation of common bit-manipulation functions

Callbacks API
ANAND

callbacks_api is a framework for registering callbacks if the callback registration function exists, else returns gracefully.

typeof
TPH

Provides functionality similar to Luau's "typeof" function

Luarocks Wrapper
lazerbeak12345

Securely Wrap Luarocks packages without needing trusted mods.