Update June 8th, 2020: As of today, an unofficial extension is available for Firefox desktop!
Hypothesis is a great web annotation tool that lets you annotate any webpage, and share your annotations publicly, within private groups, or keep them for your own.
Although webpage owners can add the necessary code to enable annotations for anyone visiting their webpages, you can annotate any webpage by simply injecting the necessary code: the Hypothesis client. To do so, the easiest way is to use a browser extension, which is currently only available for Google Chrome.
If you use other browser (e.g. Firefox, Safari) or use Chrome in your cellphone (which doesn’t accept extensions), you can still use the bookmarklet, something like a link which you can bookmark and click on any webpage to inject the necessary code to make annotations. …