Typora is not available as a web app but there are plenty of alternatives that runs in the browser with similar functionality. The best Online alternative is StackEdit, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Typora and many of them are available as a web app so hopefully you can find a suitable replacement. Other interesting Online alternatives to Typora are Roam Research (Paid), Hemingway Editor (Paid), Rentry.co (Free) and Dillinger (Free, Open Source).
As easy to use as a word document or bulleted list, and as powerful for finding, collecting, and connecting related ideas as a graph database. Collaborate with others in real time, or store all your data locally.