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Hui
Hui

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I built an AI-powered video speed controller for online courses

#ai #javascript #productivity #tools

I was taking 12 online courses in 3 months. Python, machine learning, web development — all while working full-time.

Every platform had a different video player. Udemy's speed control had 4 steps. Coursera's shortcuts were different. LinkedIn Learning didn't remember my settings. I was spending more time fighting the players than actually learning.

So I built CourseSpeed.

What it does

CourseSpeed is a Chrome extension that gives you:

  • Precision speed control (0.25x–16x) with per-platform memory — Coursera stays at 1.5x, Udemy at 1.75x
  • AI study notes — one click captures audio and generates timestamp-linked notes you can export anywhere
  • Learning analytics — shows your real efficiency, not just "hours watched"
  • Keyboard shortcuts for everything — no mouse needed

The tech stack

  • Manifest V3 Chrome extension
  • Vanilla JS (no framework — extension needs to be fast and lightweight)
  • AI note generation via speech-to-text + LLM summarization
  • All data stored locally in Chrome storage — zero server costs

What I learned

  1. Chrome's MV3 migration is painful but worth it. Service workers replace background pages, and the new API surface takes time to learn.

  2. Course platforms don't want you to control speed. Most of them strip or override custom speed controls. Getting CourseSpeed to work across Udemy, Coursera, LinkedIn Learning, and Skillshare required per-platform DOM manipulation strategies.

  3. Science backs this up. Murphy et al. (2022) found 2x speed causes no significant learning loss. Watching a lecture twice at 2x produces better retention than once at normal speed. I built CourseSpeed on this research — not assumptions.

The results so far

CourseSpeed just launched on Product Hunt and has active users on the Chrome Web Store. The most requested feature so far: per-platform speed presets (already built).

If you take online courses and want to learn faster without losing comprehension, try it out:

👉 https://joycraft.dev/coursespeed

Ask me anything about building Chrome extensions, the MV3 migration, or the science of video speed learning.

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