Eightify is one of the most popular YouTube summarizer Chrome extensions on the market. It charges $20/month for AI-generated video summaries, chapter detection, and key takeaway extraction. The functionality is genuinely useful — and genuinely simple to replicate.
This is the first in our "I Rebuilt" series. The goal: take a popular paid Chrome extension, rebuild the core functionality using PlugThis, and document the process. The pitch is straightforward — most of what paid Chrome extensions charge subscriptions for is straightforward to build once you have the right tooling.
The build
The video at the top of this post shows the full process, start to finish, in real time. 12 minutes from prompt to working extension loaded in Chrome.
The full prompt is below the video — feel free to copy it and customize for your own workflow.
What worked
The transcript fetch. YouTube exposes captions through a public API. PlugThis wired this correctly on the first generation — no debugging, no follow-up prompts. The extension fetches the full transcript when "Summarize" is clicked.
The side panel UI. The slide-in panel from the right side was generated cleanly. It's positioned correctly, doesn't break with YouTube's UI updates, and dismisses on click-outside.
The OpenAI integration. Bring-your-own-key with chrome.storage worked first try. The user's API key is stored locally, never leaves the browser, and never touches a third-party server.
What I'd customize
A few things I'd change before publishing this seriously:
- Prompt engineering — the default summarization prompt produces decent output, but tuning it for video-specific summaries (recognizing tutorials vs. interviews vs. lectures) would noticeably improve quality.
- Model selection — the prompt locks in GPT-4. Adding a settings option to switch between GPT-4 mini (cheap) and Claude Sonnet (better reasoning) would save users money.
- Caching — re-summarizing the same video re-runs the OpenAI call. Caching by video ID would make repeat views free.
Each of these is one follow-up prompt to PlugThis — total iteration time maybe 10 minutes.
The "follow-up prompt" pattern is the real superpower. You don't need to get the build perfect on the first prompt — you can iterate.
Cost comparison
Eightify costs $20/month. The rebuild costs:
- PlugThis one-time license (you already own this)
- OpenAI API usage: roughly $0.02 per summary using GPT-4 mini, or $0.10 per summary using full GPT-4
For 50 summaries per month: $1–5/month vs. $20/month. Break-even on the API costs is the first month.
The bigger upside: you own the extension. If Eightify shuts down or hikes prices, you're unaffected. If you want a feature Eightify doesn't have, you add it yourself.
Compare side-by-side
Full comparison of Eightify vs. building your own: /alternatives/eightify.
Next up
Up next in the series: WriteSeed (AI article writer). Same template — paid SaaS at top of category, rebuild in PlugThis, document the process.
If there's a specific extension you'd like to see rebuilt, reply to me on YouTube or X.