Build Story · Knowledge base for your AI · EN / KO
BrainTube: save once, query anywhere
Save the videos, podcasts, articles and PDFs you learn from. Then ask Claude, ChatGPT or any MCP client about them.
In one look
The problem
People learn from hours of video, podcasts and articles, then lose most of it. Each AI assistant keeps its own memory, locked inside one product.
What we built
Save a link and BrainTube transcribes and indexes it, with a summary, key takeaways and the people and topics in it. Ask in BrainTube's own chat, where a video citation opens at the moment it came from, or from Claude, ChatGPT, Cursor and other MCP clients, which can also save what they find.
Where it is now
Live in English and Korean: a web app, a Chrome extension and an iPhone app with an Apple Watch companion. Free to start, with $9 Starter and $19 Pro plans. An Android version is in testing.
What this would have cost in 2024
About $121k and 4–6 months
2024 team: 5–6 people: backend and AI engineer, web frontend, iOS, Android, designer with QA. Built here by one founder working with AI in 9 months.
| Piece | 2024 hours |
|---|---|
| Capture and processing: YouTube, web, PDFs, ebooks, audio, screenshots, social posts | ~667 |
| Hybrid search, knowledge graph, cited chat, search-quality gate | ~415 |
| Learning and Content Lab: reviews, quizzes, briefings, podcasts, reports | ~413 |
| MCP server with OAuth and API keys, Chrome extension | ~330 |
| Native iPhone app with widgets, share sheet and Apple Watch | ~413 |
| Native Android and Wear OS app (in testing) | ~270 |
| Plans, credits, trial, lifecycle emails, admin console | ~270 |
| Public site, comparisons and guides, Korean edition | ~270 |
| Monitoring, backups, a security pass, scaling work | ~187 |
| Total (PERT) | ~3,235 |
Method: PERT (O+4M+P)/6 per piece; low = O × $25, likely = PERT × $37.5, high = P × $50 (Accelerance 2024 Eastern-Europe band). These are estimates of what a team would have needed in 2024, not invoices.
How it was built
From first commit to current build in 9 months
- The prototype
A web app that saved YouTube videos, pulled their captions and made them searchable by keyword and by meaning. It started with a Watch Later list that had become a pile.
- Version 3.0
A larger rebuild: a transcript reader, YouTube account sync and an admin console. The busiest stretch of the build came over the next two months.
6,000+ commits, mostly automatic saves, in March and April - Learning tools and Content Lab
Spaced-repetition reviews (FSRS), graph search and deep research, plus Content Lab, which turns saves into podcasts and reports.
- Your AI can use it
A remote MCP server lets an AI assistant search the library and save into it. A Chrome extension followed three days later. Claude and ChatGPT now connect with a sign-in, no key to paste.
- A new public site
brain-tube.com rebuilt with pricing, a connect guide, comparisons and guides.
- Paid plans
A free plan, plus $9 Starter and $19 Pro with a 14-day trial and no card. Saving stays free on every plan; AI actions use credits.
- Native apps
A native iPhone app, with Android a day later: share sheet, home-screen widgets, voice questions and watch companions, on the same rules as the web app.
- A search-quality gate
A frozen set of questions is re-run against live search on a schedule, so a drop in quality is caught and reported.
search score (nDCG@10) 0.83–0.85 through late October - Korean edition
The app, the site and 71 emails in Korean. Visitors from Korea get Korean automatically, and Korean questions also search English content.
Korean search 0.944 vs English 0.963 on the same library - The iPhone app ships
The iPhone app went live in the App Store with its Apple Watch companion. Version 1.0.1 followed three days later with the app in Korean.
App Store version history: 1.0 on 27 Oct, 1.0.1 on 30 Oct
Who did what
The founder decided
- Saving is free on every plan, including saves your AI makes. AI actions use credits.
- The MCP connection comes with every plan, Free included.
- It works with any AI that speaks MCP: Claude, ChatGPT, Cursor and others, not one vendor's tools.
- Ad and analytics tags on the site load only if the visitor accepts them.
- No session recording in the iPhone app.
AI built and checked
- The web app and the public site, built in Lovable from the founder's briefs.
- Claude Code: the MCP server, the Chrome extension, the iPhone, Apple Watch and Android apps, and the Korean edition.
- The search-quality gate: test questions and relevance scores made with AI judges, re-run on a schedule.
Stack
Want something like this for your team?
From one call to something live. The same method is in the Claude Operator Pack.
From the founder
You might also like
Shares custom-domain
Shares custom-domain
Shares custom-domain