After you have built your Arduino project, you may have many hours ahead of tweaking the code until it’s perfect. It’s handy to know a few shortcuts to speed up the process. Here are the some of the most useful:

Windows/Linux Mac OS Action
Ctrl+N Cmd+N Open new sketch.
Ctrl+O Cmd+O Open existing sketch.
Ctrl+S Cmd+S Save sketch.
Ctrl+Shift+S Cmd+Shift+S Save sketch with new name.
Ctrl+R Cmd+R Compile/Verify sketch. Handy for checking the grammar of your code without uploading the sketch.
Ctrl+T Cmd+T Auto Format. Adjusts the alignment and spacing of your code to improve the legibility (but also undoes your own formatting if you’re arranging your sketch in a unique way).
Ctrl+Z Cmd+Z Undo last change to code.
Ctrl+Shift+Z Cmd+Shift+Z Redo last change to code.
Ctrl+/ Cmd+/ Comment/uncomment selected code. Useful for quickly commenting code out. Commenting a section of code means that it is not uploaded to the board, so you can use comments to quickly switch among different sections of code without having to delete them.
Ctrl+Shift+F Cmd+Shift+F Find reference page for selected code term. If you’re unsure about a highlighted term in your sketch (such as void, int, or pinMode), simply select that term and use this shortcut to be sent to the latest reference page.
Ctrl+U Cmd+U Upload the sketch to the Arduino board.
Ctrl+Shift+M Cmd+Shift+M Open the serial monitor.
Ctrl+K Cmd+K Open sketch folder.