Yamanote is a bookmarklet-based bookmarking web app. It’s a web application so you need to run it on a computer, or get a friend to run it for you. When you decide you want to bookmark a page on the web, you click on a Yamanote bookmarklet in your browser’s bookmarks bar (works great on desktop, and in Safari on iOS) to tell the Yamanote server about it. Any text you’ve selected will be added as a “comment” to the bookmark by Yamanote. This is fun because as you read, you can select interesting snippets and keep clicking the bookmarklet to build a personalized list of excerpts. You can add additional commentary to the bookmark in Yamanote, either by editing one of the excerpts made from the bookmarklet or an entirely new comment with its own timestamp. Also, the first time you bookmark a URL, your browser will snapshot the entire webpage and send it to the Yamanote server as an archive (in technical terms, it’ll serialize the DOM). This is great for (1) paywalled content you had to log in to read, (2) Twitter, which makes it hard for things like Pinboard to archive, etc. The server will download any images—and optionally videos—in your bookmarked sites. You can browse Yamanote’s snapshot of the URL (it might look weird because we block custom JavaScript in the mirror and lots of sites these days look weird with just HTML and CSS—shocking I know). Nobody except you can see your bookmarks, comments, or archives.

Populus-Viewer is a tool for decentralized social annotation, built on pdfjs, wavesurfer.js and the Matrix protocol. You can use it to read PDFs, listen to audio, or watch videos, and have rich discussions in the margins, with your friends, classmates, or scholarly collaborators.

Each uploaded file is attached to a matrix space, and each annotation to the file becomes a room within that space. Populus-Viewer has been tested with synapse and dendrite, but should be compatible with any spec-compliant matrix server.

An online bookmark manager which also can act as a content archiver. Can save content as HTML, PDF, or PNG in addition to storing links for later reference. Automatic summarization and tagging of links. Multiple user accounts. Multiple back-end databases (SQLite default). Annotation support. Written in Python 3. Don't know if there's an API.