Promnesia by Dima Gerasimov

Promnesia is a browser extension (Chrome/Firefox/Firefox mobile) which provides a sidebar which complements browser history with some enhanced features.

TLDR: it lets you explore your browsing history in context: where you encountered it, in chat, on Twitter, on Reddit, or just in one of the text files on your computer.
This is unlike most modern browsers, where you can only see when you visited the link.

It allows you to answer different questions about the current web page:

• have I been here before? When?
• why have I bookmarked it?
• how did I get on it? Which page has led to it?
• who sent me this link? Can I just jump to the message?
• which links on this page have I already explored?
• which posts from this blog page have I already read?

NOTE: to get the most benefits from the extension, you also need to set up a supplementary service. You can find the instructions here.