Data and APIs

If you build your own models, scripts or dashboards, you need data you can pull programmatically. The services here range from free public economic data to paid market data feeds, and most offer an API with a free key for light use.

Start with what you need: daily prices or intraday data, fundamentals, estimates, options, economic series or alternative data. Then check history depth, exchange coverage and how each provider handles splits, dividends and restatements. Two providers can return different numbers for the same company because they define or adjust a measure differently.

Read the license as carefully as the documentation. Free and low-cost plans often restrict use to personal projects and forbid showing the data to others or using it commercially. Real-time exchange data usually carries extra exchange fees and agreements.

Check rate limits and reliability. A free key that allows a handful of calls a minute is fine for a weekly model and painful for a dashboard. Look at status pages and changelogs, since endpoints and plans change over time.

Point-in-time data matters for backtests. Many datasets show today's revised figures for past periods, which makes a strategy look better than it could have been in real time. If you test ideas on history, ask whether the provider offers data as it was first reported.