Open Gmail
Select the checkbox at the top of the inbox
Click “Select all conversations in Inbox” if shown
Click the trash icon to delete selected emails
To archive instead, click the archive icon
To delete all emails in a category, open that category and repeat the steps
To remove emails permanently, open Trash and click “Empty Trash now”
To clear spam, open Spam and click “Delete all spam messages now”
To empty the inbox without deleting, use search filters and archive or move emails in bulk