Google Fonts is a library of over 800 libre licensed fonts, an interactive web directory for browsing the library, and APIs for conveniently using the fonts via CSS. The directory was launched in 2010. Popular fonts in Google Fonts include Open Sans, Roboto, Lato etc... The library is maintained through Google Fonts' GitHub repository.
Best Google Font Alternatives
Fontsquirrel has thousands of handpicked free fonts for pc and web.
The Fonts.com store from Monotype offers more than 150,000 desktop and Web font products for you to preview, purchase and download
3) Adobe Typekit
Typekit is an online service which offers a subscription library of high-quality fonts. The fonts may be used directly on websites or synced via Adobe Creative Cloud to applications on the subscriber's computers. Typekit was launched in November 2009 by Small Batch, Inc. A company run by creators of the Google Analytics service. In October 2011, the service was acquired by Adobe.
Fontspring is a unique font license distributor. Fonts licensed from Fontspring are yours to use on as many projects as you like. No annual fee. You can try the font in any program for testing before buying.
5) Envato Fonts
Envato Elements. An unlimited, subscription-based design platform powered by a community of independent designers. Unlimited downloads for a single fee. Powered by a community of independent designers. One simple commercial license for all content.