thumbalizr is described as 'Lets you take thumbnail screenshots of any webpage and save it on your PC. No sign-up required, just enter the website URL and press the “thumb it” button'. There are four alternatives to thumbalizr, not only websites but also apps for SaaS. The best alternative is CrossBrowserTesting. It's not free, so if you're looking for a free alternative, you could try Miniature.io or PagePeeker.com.
The all-in-one web testing platform supports manual, visual, and automated testing across more than 1500 different desktop and mobile browser configurations. Test on Safari, Internet Explorer, Android, iOS, and more.
Put website thumbnails and favicons on your site. Free branded (up to 480x360), free unbranded, paid versions. Fast servers and lots of impressions. + Quick implementation + Scales automatically for you + Cheaper than doing it yourself + 99.