Uncheck the checkbox next to “Show verbose output during: compilation”
Check the checkbox next to "Show verbose output during: upload
Sketch > Upload
After the upload fails, you’ll see a button on the right side of the orange bar “Copy error messages” (or the icon that looks like two pieces of paper at the top right corner of the black console window in the Arduino Web Editor). Click that button.
In a forum reply here, click on the reply field.
Click the </> button on the forum toolbar. This will add the forum’s code tags markup to your reply.
Press “Ctrl + V”. This will paste the upload output between the code tags.
Move the cursor outside of the code tags before you add any additional text to your reply.