JEI

JEI, or Just Enough Items, is a utility mod made by mezz. JEI is a popular mod that has been included in many modpacks created since Minecraft 1.8. Similarly to NEI, JEI modifies the existing Inventory GUI by adding an icon list of items to the far right. This list can be searched via a text box at the bottom. This list is useful for checking recipes and uses for items, and can also be used to search for items in opened GUIs. JEI has a lot of addons, generally adding extra modded recipe support like Thaumic JEI.

Using JEI
JEI's search box can be seen from (almost) any GUI in the bottom right of the screen. Hovering over an item and pressing the "R" key (for Recipe) will display that item's recipe while pressing the "U" key (for Use) shows what that item can be used to create through crafting grids. Both of these keys can be changed in the mod's config file. Double-clicking the search box will visually filter any inventories, including all chests for items that match the search field's criteria. Items that do not match the current search will be grayed out. Double-clicking again will turn off the search mode.

There are 2 arrow buttons above the item list. Clicking on the right one will take the player to the next page, while clicking the left one will take the player to the previous page (if one exists). To toggle the icon list of items, press "Control + O."

Multiple terms can be looked for in the search field by separating them with the "|" character. For example:  will show everything with pickaxe and/or axe in its name.

To select the search box without clicking on it, the player can press Control + F.

Configuration
To open the config menu, click the wrench in the bottom right of the item list. This will bring up a menu displaying all the config options. The following tables will explain these options:

Both menus have buttons at the bottom, "Reset to Default" and "Undo Changes", Reset to Default resets all the options to the defaults, and Undo Changes will undo the most recent changes the player has made.