Photoshop Hotkeys

General

Function	Key	Notes
Brush Settings (menu)	`Window > Brush Settings`
Tool Preset (menu)	`Window`
Adjust Brush Size and Hardness	`Alt` + `Right Click`	Move mouse horizontally to change size and vertically to change hardness
Adjust Brush Opacity	`1 - 0`	`1` is 10%, `9` is 90% and `0` is 100%
Undo	`Ctrl` + `Z`
Redo	`Ctrl` + `Shift` + `Z`

Tools

Function	Key	Notes
Brush	`B`
Eraser	`E`
Lasso	`L`
Eyedropper	`Alt`
Clone Stamp	`S`
Spot Healing	`J`

Interface

Function	Key	Notes
Hide All Panels	`Tab`
Hide Right Panel	`Shift` + `Tab`

Layers

Function	Key	Notes
New Layer	`Ctrl` + `Shift` + `N`
Duplicate Layer	`Ctrl` + `J`	Works with tools
Merge Layer Down	`Ctrl` + `E`	When multiple layers are selected, all are merged together
Group Layers	`Ctrl` + `G`
Ungroup Layers	`Ctrl` + `Shift` + `G`
Create Layer Using All Selected Layers	`Ctrl` + `Shift` + `Alt` + `E`

Selecting

Function	Key	Notes
Select All Pixels On Layer	`Ctrl` + `LMB` (on layer thumbnail)
Select All	`Ctrl` + `A`
Deselect All	`Ctrl` + `D`
Reload Last Selection	`Ctrl` + `Shift` + `D`
Inverse selection	`Ctrl` + `Shift` + `I`
Add To Selection	`Hold Shift`
Remove From Selection	`Hold Alt`

Transforming

Function	Key	Notes
Move Tool	`V`	Click and pull around any layer
Image Size (window)	`Ctrl` + `Alt` + `I`
Transform Object	`Ctrl` + `T`	More advanced version of move tool. Doesn’t work on locked layers
Scale Object from Center	`Hold Alt` (Transform Mode)
Scale with Free Aspect Ratio	`Hold Shift` (Transform Mode)
Pull Transform Points	`Hold Ctrl` (Transform Mode)

Dialog Boxes

Function	Key	Notes
Reveal Reset Button in Menus	`Hold Alt`

Function	Key	Notes
Rotate View	`R`	Holding`R` will revert to the previous tool when let go.
Move View	`Hold Space` or `H`	Holding `H` will revert to the previous tool when let go.
Zoom in / out	`Hold Alt` + `Scroll Wheel` or `Ctrl` + `+` / `-`
Switch to Next Image	`Ctrl` + `Tab`
Switch to Previous Image	`Ctrl` + `Shift` + `Tab`
Maximize View	`Ctrl` + `0`

Other

Function	Key	Notes
Reset Colors	`D`	Resets foreground and background colors to default
Cycle Active Color	`X`	Flips foreground and background color
Fill Selection With Foreground Color	`Alt` + `Backspace`
Fill Selection With Background Color	`Ctrl` + `Backspace`
Desaturate Image	`Ctrl` + `Shift` + `U`
Export (window)	`Ctrl` + `Shift` + `Alt` + `W`
Save As (window)	`Ctrl` + `Shift` + `S`
Straight Line	`Shift`
Layer Style (window)

https://helpx.adobe.com/photoshop/using/default-keyboard-shortcuts.html