Screenshot Guru is an excellent app for taking complete screenshots of websites you want. You can take screenshots of the whole website online. The images are high resolution and are available in PNG format.

The user interface, it's smooth and easy to use the tool.

Screenshot Guru makes it easy to take a screenshot of an entire webpage that is publicly accessible online. To take a screenshot, one only needs to enter the web address of the webpage, click the Google reCAPTCHA checkbox, and click the button labeled “Screen Capture” button, after which Screenshot Guru will generate a downloadable PNG image of the whole webpage. Screenshot Guru captures a screenshot of the entire webpage, unlike the Windows 10 Snipping Tool. With the latter, screenshot captures only include the part of the webpages that is immediately displayed on the visitor’s monitor, while the parts of the webpage that are offscreen (e.g., below the fold) cannot be captured. Use of Screenshot Guru is free of charge.