Glasp

Glasp is a highlighter that refuses to treat reading as a purely private act. It works as a free browser extension that marks up web pages and PDFs, collects those marks in your own profile, and — the design choice that defines the product — shows much of it publicly, so other people highlighting the same passage can appear on the page as you read it, colour-coded by who made the mark. The accumulated notes form a personal library that behaves like a study diary, and Glasp layers AI passes over that material, summarising long pages and video transcripts so a highlight becomes a starting point rather than a relic. It is not a reader and not a read-later queue; the page itself is where things collect.

The caveat is about evidence rather than opinion: the vendor site refused automated reads when this entry was refreshed, so the current shape of the AI features, the account model and the public-by-default behaviour should be confirmed at glasp.co before you rely on them. Two things deserve checking regardless. Public-first is a strong identity and a poor fit if you read anything sensitive; and since the value of highlighting only appears in bulk, verify that the export path actually works before a year of reading has accumulated behind it.