If you want to see what your website looks like in different browsers, you can use browserstack, one of the best options in that category, but if you want to capture a complete web page, I recommend snapito.com, a simple solution, fast and with excellent results.
Without registration, you just have to enter the url and wait for the image to be generated, which can be downloaded to the computer and easily shared. Snapito’s business model is attractive: they offer a service that captures and thumbnails for any website, with a free price for less than 50,000 monthly impressions. If you play a directory of websites, for example, you can use their service to capture the pages, or if you play a mobile application, you can choose a plan for this type of device.
Personally I use Snapito to verify the appearance of any website taking the guarantee that it does not take into account the files saved on my computer (cached css files, for example, or other browser temporary files). Although browserstack is more efficient for that type of work (try multiple browsers), Snapito is faster, and sometimes that’s exactly what is needed: agility.