Mac users can use the keyboard combinations to take screenshots and capture anything displayed on their computer screen. Press Shift-Command (⌘)-3 to take a screenshot of entire screen, press Shift-Command-4 to select an area and capture. You can find more details from this Mac screen capture guide. When browsing the web, you will find you have to scroll down to see the entire web pages sometimes. The webpages are too long to be displayed in one screen, thus you can’t capture the entire page in a single screenshot. Fortunately Firefox browser has the built-in screenshot feature that can help us easily screenshot entire webpage or capture full web pages on Mac. Check out the steps with screenshots below.
Open the web page you want to capture in Firefox for Mac OS. Right click on any blank area on the page, choose Take a Screenshot from the contextual menu that pops up. At the upper right corner, you have the options to capture and save full page or the visible part of the page. You can also drag on the page to select a region to capture. Choose Save full page, see below screenshot.
After that you will have the options to copy the screenshot to clipboard, save it to the Downloads folder on Mac or upload to the cloud hosting service so you can access the screenshots or share with other people through URLs.
On the screenshot save menu, click the Download button, the captured web page screenshots will be saved as JPEG files to the Downloads folder on Mac. If you like, you can open the web page screenshots in Preview and convert them to HEIF, PNG, PDF, TIFF or other formats.