Lesson summaries

A published lesson can be summarized on your own computer, so you can tell at a glance what a lesson covers before reading it end to end. Nothing is sent to a server: the summary is written by an AI model running in your browser.

Making a summary

On a lesson's Lesson tab, a Summary card with an On-device AI badge sits above the lesson.

1. Pick a style and a length if you like:
   • Style: Key points (a bulleted list, the default), TL;DR, Teaser or Headline.
   • Length: Short (the default), Medium or Long. These are relative sizes, not word counts.
2. Press Summarize. The summary writes itself into the card as the model produces it, and Cancel stops it.
3. Copy summary copies it. Regenerate writes a new one.

Changing the style or length clears the summary, so what's on screen always matches the menus. Press the button again to write one in the new shape.

The first time

The first summary on a computer has to download a model, once:

• In Chrome or Edge, the browser's own built-in AI model. The card says the first summary downloads it and can take a while. Chrome needs about 20 GB of free disk space to install it. If the download never starts, the card moves on to the open model below where your computer can run it, or says the download didn't start.
• Everywhere else, an open AI model called LFM, about 760 MB. The card says so before you press the button, so you never start that download by surprise.

A progress bar shows the download. After that the model stays saved in your browser, and summaries start much faster. To free the space, go to Settings, find Downloaded AI models and press Delete models. Your lessons aren't affected. (Chrome's own built-in model belongs to the browser and isn't removed this way.)

When the card doesn't appear

The card hides itself rather than showing a button that can't work. You won't see it when:

• your browser and computer can't run either model (for example, an older graphics card, or a browser without the features the open model needs),
• your browser says you're on mobile data or have data saver turned on, so you don't get a large download by accident, or
• the lesson is very short, since a summary would be about as long as the lesson.

Language

The summary is written in the lesson's language where the model can manage it. Chrome's built-in model can write German, English, Spanish, French and Japanese. The open model can write English, Arabic, Chinese, French, German, Japanese, Korean and Spanish. A lesson in any other language, or one whose language your browser can't tell, gets an English summary. In browsers other than Chrome and Edge, summaries are usually in English.

Trust it, but check

Under the summary, a note says it was generated on your device (and by which kind of model) and that it can be wrong. The lesson itself is always the source of truth. A long lesson may be too big for the model to read in one go; then it summarizes the first part, and the note says so.

For how summaries work in the code, see the developer notes.