Inking in OneNote Online

Microsoft is bringing inking and the Draw tab to OneNote Online, so you can make your mark with ink or highlighter while taking, reviewing, or editing your notes in the browser.  

Whats-new-for-office-365-March-5

OneNote works the way you do, with new inking capabilities in the browser.

Availability: Inking is rolling out for all customers using OneNote Online in Microsoft Edge, Internet Explorer, Firefox, Safari and Chrome.