Photoshop is full of keyboard shortcuts. Many of them are hidden from the user. Here are some of the most useful shortcuts to learn.
Working with tools
| Mac | Windows | |
|---|---|---|
| Larger/smaller brush | Ctrl + Option + drag left/right | Right Mouse + Alt + drag left/right | 
| or left/right brackets [ and ] | ||
| Harder/softer brush | Ctrl + Option + drag up/down | Right Mouse + Alt + drag up/down | 
| Temporarily access Move tool with other tool active | Command | Ctrl | 
| Temporarily use Dodge when using Burn tool | Option | Alt | 
| Move, Marquee, Lasso, Pen tools | V M L P | |
| Brush, Stamp, Burn, Healing tools | B S O J | |
| Change brush strength to 10%, 20%...100% | Number keys 1, 2 … 0 | |
| Change brush strength to eg 35% | Number keys 3 then 5 | |
| Temporarily access Polygonal mode with Lasso tool | Option | Alt | 
Working with selections
| Mac | Windows | |
|---|---|---|
| Before drawing selection: | ||
| Add to previous selection | Shift | |
| Subtract from previous selection | Option | Alt | 
| Intersect with previous selection | Shift + Option | Shift + Alt | 
| While drawing selection: | ||
| Constrain to square/circle | Shift | |
| Draw from centre out | Option | Alt | 
| Move selection while drawing | Spacebar | |
Viewing channels
| Mac | Windows | |
|---|---|---|
| View red/green/blue channel | Command + 3/4/5 | Ctrl + 3/4/5 | 
| View RGB channel | Command + 2 | Ctrl + 2 | 
Working with layers
| Mac | Windows | |
|---|---|---|
| Move layer up/down | Command + [ ] | Ctrl + [ ] | 
| Select layer up/down | Option + [ ] | Alt + [ ] | 
| Nudge layer 1 pixel (with Move tool) | Up/down/left/right arrows | |
| Nudge layer 10 pixels (with Move tool) | Shift + up/down/left/right arrows | |
| Cycle through layer modes | Shift + plus / minus keys | |
| Fill with foreground color | Option + Backspace | Alt + Backspace | 
| …preserving transparency | Shift + Option + Backspace | Shift + Alt + Backspace | 
| Fill with background color | Command + Backspace | Ctrl + Backspace | 
| …preserving transparency | Shift + Command + Backspace | Shift + Ctrl + Backspace | 
| Open Fill dialog | Shift + Backspace | |
| Set colors to default black/white | D | |
| Swap foreground and background colors | X | |
| Lock layer transparency | / | |
| Enter/Exit QuickMask | Q | |
| Copy Merged | Command + Shift + C | Ctrl + Shift + C | 
| Change layer opacity to 10%, 20% … 100% | 1, 2 … 0 | |
| Change layer opacity to 0% | 0 0 | |
| Change layer opacity to eg 35% | 3 then 5 | |
Working with dialogs
| Mac | Windows | |
|---|---|---|
| Load with previous settings | Option + menu | Alt + menu | 
| Increase/decrease values | Up/down arrows | |
| Increase/decrease values x10 | Shift + up/down arrows | |
| Toggle Preview on/off | P | |

