Highlights text and clicks any element, keeps private ("Mine") and public ("World") notes on the original page, exports to Obsidian and Notion, and ranks the web’s most-discussed sites.

Best for: Readers who want their marks to stay on the page, plus a public layer they can browse.

Open-source annotation with public/private groups and a real API. Free at every scale.

Best for: Educators, researchers and anyone building annotation into their own workflow.

Private-by-default highlighting organized into folders, with PDF support.

Best for: Students running structured literature reviews across many sources.

Social highlighter with a follow feed — highlighting as a public activity.

Best for: People who want their reading to be social and discoverable.

Read-it-later app that consolidates highlights from articles, feeds and ebooks.

Best for: Heavy readers who want one unified highlight inbox with spaced repetition.

Social reading with friends — shared books, shared highlights.

Best for: Book clubs and friend groups that read together.

Bookmark manager with highlights and notes attached to saved links.

Best for: Collectors who organize everything by link and want annotations alongside.