There are a few ways to take a screenshot of a whole web page:

Using the built-in screenshot tool in your browser: Most modern web browsers such as Google Chrome, Firefox, and Safari have a built-in screenshot tool that allows you to capture the entire web page. Look for the three dots or the hamburger icon on the top right corner of the browser and look for the option "screenshot" or "take a screenshot"

Using the keyboard shortcut: On a Windows or Linux computer, press the "Ctrl" and "Shift" keys and then press "S." On a Mac, press the "Command," "Shift," and "4" keys, then press the spacebar and click on the browser window.

Using a third-party extension: There are many third-party browser extensions available for taking screenshots, such as Nimbus Screenshot and Lightshot. These extensions allow you to capture the entire web page and also provide additional features such as annotation and editing.

Using a screenshot tool like Lightshot

Using a command-line tool like wkhtmltoimage that renders a webpage as an image by using webkit rendering engine.

Take a full-page screenshot in mobile devices by taking screenshots in the scrolling mode.

Keep in mind that some web pages may have content that is not visible on the screen, such as content that is below the fold or content that is hidden behind a login. In these cases, the screenshot may not include all of the content on the web page.