Crypto Checker

A personal, informational-only scanner. Click Scan market and it checks every liquid USD pair on Coinbase. It then shortlists the coins that are down now but have rebounded from similar dips before, with charts for researching each one. There is no trading, no API keys and no backend.

Run it

npm install
npm run dev        # open the printed localhost URL

Other scripts: npm test (vitest), npm run typecheck, npm run build then npm run preview.

How it works

1. Universe. Coinbase /products and /products/stats supply every online USD pair. Stablecoins, pegged assets, wrapped and liquid-staking tokens, and coins under the minimum daily volume are skipped. CoinGecko's keyless /coins/markets adds names, logos, market-cap rank and ATH. It is optional: if it is rate-limited, the last copy (cached for 30 minutes) is used.

2. Screen. Each coin's last ~350 daily candles give its drawdown from the 1-year high, RSI, Bollinger %B, SMAs and a preliminary score. A coin qualifies if it is ≥25% below its 1-year high or ≥15% below its 90-day high.

3. Deep history. The top 50 candidates get up to ~2,100 days of history. The app finds every past time each coin was about this far below its 1-year high and measures what happened over the next 30, 90 or 180 days:

   • hit rate
   • median return
   • worst drop first
   • whether it regained its prior high
   • edge against buying on any random day

4. Score (0–100).

   • track record 35%
   • unusual depth 25%
   • oversold 15%
   • not a falling knife 15%
   • liquidity 10%

   The total is scaled by how many comparable dips back it up, and a coin down 90%+ in a year is marked down as a likely collapse rather than a dip. The in-app "How the score works" panel has the details and caveats.

Daily candles are cached in IndexedDB, so the first scan takes about a minute and later ones a few seconds. Reopening the page shows the last results straight from the cache.

Layout

• src/api: rate-limited Coinbase client, CoinGecko client, IndexedDB cache
• src/analysis: indicators, analog/episode analysis, metrics, scoring, universe filters (all unit-tested in tests/)
• src/scan.ts: the staged scan pipeline
• src/ui: table, detail view, settings, progress, and the ECharts charts in src/ui/charts

Informational only, not financial advice.