What is a second brain app?

A second brain app is software for capturing and retrieving the information you would otherwise forget — articles, videos, highlights, notes, and ideas. The name comes from the productivity practice of offloading memory to a trusted external system: instead of trying to remember everything you read, you save it somewhere reliable and let the system do the remembering. A good second brain app makes capture instant and retrieval dependable.

The two jobs: capture and retrieval

Every second brain lives or dies on two things. Capture has to be frictionless — one click, no decisions about where things go — or you stop doing it within a week. Retrieval has to work even when you’ve forgotten the title, the source, and whatever label you might have used. Most systems fail on the second job: links and notes pile up in a tool that can’t surface them, which is storage, not a second brain.

Note-first vs save-first tools

Second brain apps split into two families. Note-first tools center on writing and linking your own notes, with web content clipped in as raw material. Save-first tools center on capturing what you read and watch on the web, then organizing and retrieving it automatically. What is a second brain app? breaks down the landscape, and what is an AI second brain? covers how AI changed the category — automatic organization and retrieval by meaning replaced manual tending.

How Marqly approaches it

Marqly is a save-first second brain built as an AI bookmark manager. Capture is one click from the browser extension; you can also highlight text on any page in six colors and attach notes, and the highlights sync to your library. Retrieval is where the AI earns its keep: every save is auto-tagged, articles get AI summaries, and semantic search finds saves from a half-remembered description. On the Pro plan you can go a step further and chat with your saved content — ask a question, get an answer drawn from what you’ve saved.