KeJi 课迹

Take notes while a lecture plays. Click one to go back to that second.

KeJi is a small Chrome / Edge extension. Every note remembers the moment in the video. When you review, click it and the video jumps back to the second you wrote it.

Download KeJi 0.4.0 (zip) How to install

Free · No sign-up · Notes stay in your own browser · Chrome and Edge on Windows / Mac

Lecture 7 · The derivative as a slopef′(x₀) = lim (f(x₀+h) − f(x₀)) / h
12:14 / 45:10
KeJiPlaying

    This demo is live: the video pauses when you start typing. Click a time or a paw on the progress bar to jump back.

    One job, done well: keep the second, then bring you back

    Like a corgi that fetches.

    Write as you watch

    Saving keeps the video’s current time. The video pauses when you start typing and resumes after you save, so you don’t miss anything.

    Click to jump back

    Click a note’s time, or a paw on the progress bar, and the video returns to that second. If the page is closed, KeJi reopens it and waits for the video.

    Never in the way

    Choose a popup, a floating panel or the side panel. The floating panel drags and folds; the side panel makes room so the whole video stays visible.

    • Speed 0.5–2×
    • Alt+Shift+N notes in fullscreen
    • Notes grouped by video
    • Search and mark to review
    • Export to Markdown (times are links)
    • Right-click to save a question
    • English / 中文
    • Dark mode

    What it looks like

    Light and dark follow your system. It fits in on YouTube.

    KeJi popup: playback status, progress bar with paws, note box and this page’s notes
    Popup: each paw on the bar is a note
    KeJi settings in dark mode: layout, pause while typing, remember speed
    Settings live behind the gear (dark)
    All notes page, grouped by video, with search and export
    All notes: grouped by video, searchable, exportable

    Install (about 3 minutes)

    KeJi is not in the extension store yet, so you load it once in Developer mode.

    1. Download and unzipDownload the zip and unzip it. Move the keji folder somewhere permanent, such as Documents.
    2. Open the extensions pageIn Chrome type chrome://extensions in the address bar. In Edge type edge://extensions.
    3. Turn on Developer modeTop right in Chrome, left side in Edge.
    4. Load the extensionClick “Load unpacked” and choose the keji folder itself.
    5. Pin the corgiClick the puzzle icon in the toolbar and pin KeJi.
    6. Reload your lecture pageReload any video page that was already open. That’s it.

    Shortcuts

    • Alt+Shift+C open KeJi
    • Alt+Shift+K play / pause
    • Alt+Shift+N take a note on the page (works in fullscreen)

    On Mac, Alt is Option. If a key does nothing, set it at chrome://extensions/shortcuts.

    What it never does

    • Change watch time, progress or completion
    • Answer or submit anything, or ask for a password
    • Send your notes anywhere: there is no server

    If the browser asks you to disable developer-mode extensions at startup, choose Keep. To upgrade, unzip over the old folder and click reload on the KeJi card. Your notes are kept.