Stock and crypto research on web and iOS
StockMarketCap is a website and iOS app for researching stocks, crypto, and fund holdings. It converts prices to USD so users can compare assets across different markets.
I built the apps, data pipeline, and subscription system. I also handle marketing, including software that creates daily social posts from the site’s data.
View project →Market rankings
The site ranks 5,700+ stocks and ETFs across nine markets, alongside roughly 965 cryptocurrencies. Prices are converted to USD for comparison.
Research tools
Users can filter stocks, test historical returns, track a portfolio, and set price alerts. Research pages include financial statements, dividends, forecasts, fund holdings, and reported trades by insiders and members of Congress. A search assistant answers questions using the site’s data.
iOS app
The iOS app includes market rankings, portfolios, watchlists, and alerts. I built it with React Native and Expo and set up over-the-air updates between App Store releases.
Automated social posts
I built a system that creates daily X posts and Instagram carousels from the site’s data. A language model writes the text, and a validator checks its figures before publication. Each post includes an image generated from the same data.
Charts on web and iOS
I built charts with a fill that fades into pixels below the line. The website, iOS app, and social images use the same style.
Engineering notes
Currencies and trading hours
The data pipeline handles currencies and trading hours across nine markets and 19 exchange calendars. It converts prices to USD and refreshes quotes every minute.
Shared data model
Stocks, ETFs, and cryptocurrencies use the same data model and charts, including support for prices below one cent.
Fund holdings
The site reads public SEC 13F filings to show a fund’s reported holdings and changes between quarters.
Validating generated figures
The model writes prose using approved figures from production data. A validation step rejects numeric claims outside that set before publishing.
iOS charts
I recreated the website’s Canvas chart fill in Skia for iOS.
Page caching
Stock pages are cached and regenerated periodically. Subscription access is checked separately in the browser.
Result
The website and iOS app are live, with free features and a paid subscription. I develop and maintain both.
Testing formats, voice, and posting schedules doubled the X audience and lifted engagement per post by about 40%. The app grew to hundreds of users in its first months.
Social posts are generated from the site’s data and checked before publication.