McJtyLib is a library used by many of McJty and romelo333 mods. It provides common libraries many mods use, especially in the RFTools series.
 
McJty is most known for its modding tutorials, and they make many modding tutorials for Minecraft forge covering many topics. They are one of the top Mod Making tutorial makers. They are also involved in many popular mods. McJtyLib is behind many of them. Some of the great things it allows you to expand upon include the following:

Power
Smartwrench
Containers
Modules
Information
Config
Styleised Config
Bindings
Blocks
Block Commands
ToolTips
Info Lines
Rendering
GUI
Huds
Models
Compatibility with Various mods such as Patchouli, JEI, Walia, The One Probe, and More
Crafting
Data Generation
Debugging
Font
Keys
MultiBlocks and Multiparts
Network
World Data
And Much, much more

It is for Minecraft Forge only, which is something to remember. It is MIT Licence, so you can easily use it for your mods without legal issues. However, the source is not made too easy to find by default but can be found here https://github.com/McJtyMods/McJtyLib

Some mods which use McJtyLib include

Aqua Munda
Ariente
Ariente World
Deep Resonance
EFab
Elemental Dimensions
Fancy Trinkets
Gear Swapper
GuGu Utils
HoloGui
Immersive Craft
MeeCreeps
Mystical Enhancements
Naberius - The Demon Realm
Need to Breathe!
Not Enough Wands
Quest Utils
Restrictions
RF Lux
RFTools
XNET
And More

newest

fresh

relevant

playable

legacy

McJtyLib Mod