Options need their own data. If that’s your interest, Market Data App is built around U.S. options chains with simple REST endpoints. For historical options and volatility research, you can buy straight from the exchange operator behind the VIX through Cboe DataShop. Futures and commodities are covered by Barchart OnDemand, a business-grade set of APIs.
Two newer names round things out. In 2024, Finage pitched itself as an IEX Cloud replacement. There’s also Eulerpool, with a free plan for quotes and fundamentals. Its marketing leans on comparison articles in which it ranks itself, so trust your own testing over those rankings.
- Ingest data
- Store it
- Evaluate rules
- Send alerts
- Display
A stock monitoring platform can be a weekend Python script or a polished dashboard. Either way it does five jobs, and every financial API you’ll come across fits one of them.
Single stocks rarely move alone. A surprise inflation reading can move the whole market in minutes, so a small macro panel next to the watchlist earns its space. The best sources here are free and come from government.
Where Your Prices Come From
If you already use PostgreSQL, add TimescaleDB. It’s an open-source extension, so you keep SQL and gain fast time-bucketed queries. The company behind it renamed itself from Timescale to Tiger Data in June 2025, and the extension kept its name. A purpose-built alternative is InfluxDB, open source or cloud, widely used for metrics and market ticks. For very high ingestion rates, there’s QuestDB, which is open source and aimed at financial tick data.
Free Tiers to Learn On
Use two data providers and small mismatches start causing bugs. One writes Berkshire Hathaway’s class B shares as BRK.B, the other as BRK-B. A scheduler that doesn’t know about market holidays will burn quota polling a closed exchange.
Some of the best alternative data costs nothing. Form 4 filings show insiders buying and selling, and 13F filings show what large institutions held each quarter. Both come through EDGAR. The paid providers sell them already cleaned up.
Then there’s Tradier, a brokerage built around its API, which a number of independent trading apps run on. And if you want to test the whole path from alert to order without real money, Alpaca’s trading API gives you a free paper-trading account.
Live Data Without a Large Bill
The second comes from a broker. Alongside its commission-free trading API, Alpaca offers a free data plan with real-time U.S. stock prices from a single venue, streamed over WebSockets. One venue means you see that venue’s trades only, so prices can drift a little from the consolidated quote. For a personal dashboard that rarely matters. If your platform might place trades later, starting here also saves you a migration.
Price tells you what happened. For why, you need fundamentals, and Financial Modeling Prep is where a lot of developers went after IEX Cloud shut down in 2024. It pairs price history with financial statements and insider activity. The free plan was listed at 250 calls a day as of mid-2026.
When the Story Is in the Financials
SMS usually means Twilio, billed per message, which also handles voice and WhatsApp. Push is cheaper and just as quick. For personal use, Pushover costs little: send one HTTP request and the alert lands on your phone, with priority levels for the moves that matter. The open-source equivalent is ntfy, which you can use hosted or run yourself, and an alert is a single request to a topic URL. If you’ve built your own app, Google’s free Firebase Cloud Messaging handles push to phones and browsers.
Stock apps show what their designers decided matters. Build your own and you choose what to watch and when to be told. This guide covers the services people use for each part of the job.
For a live dashboard on no budget, look at Finnhub. It streams prices over WebSockets on its free tier, which very few providers do, and it bundles news and fundamentals with the quotes. International coverage needs a premium plan.
When Your Watchlist Crosses Borders
At the serious end, Databento sells exchange-grade tick data and full order books, priced by usage. There’s no permanent free tier. New accounts get a one-time credit to evaluate it, and most of its users are quantitative developers. Few hobbyists will buy from Intrinio, which sells its marketplace of datasets mainly to businesses, but its terms are a useful look at what commercial licensing involves.
General news takes more work. With NewsAPI you filter by company name yourself, and its free plan isn’t allowed in production. The GDELT Project is a huge free dataset of world news coded for tone. It’s more useful for macro and geopolitical signals than for one company’s headlines.
Options, Futures, and the Specialists
That standard is still Bloomberg, delivered through B-PIPE and its other data products, usually alongside a Bloomberg Terminal. The former Refinitiv now sells real-time feeds and deep history as LSEG Data & Analytics.
For finance news tagged by ticker, Benzinga has structured news alongside analyst ratings, and it’s also available through Massive. A lighter option is Marketaux, which adds sentiment scores for each company named in an article and has a free tier.
U.S. data is everywhere. Outside the United States, coverage is what separates providers. For a portfolio spread over several countries, EODHD has end-of-day prices and fundamentals for many international markets, along with the exchange calendars you’ll need anyway. A simpler option is Marketstack from APILayer, a plain REST API covering more than 70 exchanges. Its free plan is tiny at 100 requests a month, but the paid tiers are cheap.
A Word About yfinance
Data is the hard part. You can write your own alert logic and charts, but you can’t write market data, and that’s where cost and licensing get decided. So most of this guide is about getting prices in. The sections on storage, alerts and charts come later and are shorter.
Let Your Broker Supply the Data
For crypto prices across exchanges, CoinGecko has a free demo tier and CoinMarketCap a free basic plan. If you want data straight from an exchange, the Binance API streams market data for free where Binance is available. U.S. developers often use the Coinbase Developer Platform instead.
If your interest is research more than live quotes, try Nasdaq Data Link, which used to be Quandl. Its catalog mixes free and paid datasets, and next to the equity data and fundamentals sits a long list of economic series.
Asian markets are harder to cover. Based in Hong Kong, iTick covers stocks in several Asian markets, including Hong Kong and mainland China, as well as the U.S., and it offers FIX connections next to REST and WebSocket. It’s newer than most services here. We’d test it properly before relying on it.
Going to the Source: Regulatory Filings
An alert tells you something happened. A headline next to it tells you why, and plenty of commercial apps still don’t do this well.
Backtesters tend to like Tiingo, which is known for reliable end-of-day history going back decades at a low price. It has intraday IEX data and news too.
When a stock moves sharply on no obvious news, the explanation is often in a filing. Add filings data and your platform can flag a new quarterly report or an insider trade once it’s filed.
The Bigger Picture: Macroeconomic Data
The most capable option is the Interactive Brokers API, with real-time market data subscriptions and order routing to markets worldwide. It also takes the longest to learn. Schwab customers get the Charles Schwab Developer Portal, which replaced the old TD Ameritrade API, though you’ll need to register your app and wait for approval.
Among general-purpose libraries, Apache ECharts supports candlesticks and copes well with large datasets. Candlesticks need a plugin in Chart.js, so we’d keep it for allocation and performance charts.
Explaining the Move: News and Sentiment
Almost every Python stock tutorial uses yfinance. It’s free and easy. It also isn’t an official API: the library relies on Yahoo Finance’s internal endpoints, so it breaks without warning when Yahoo changes them, and using it may conflict with Yahoo’s terms. For learning, that’s an acceptable risk. On anything you depend on, a broken endpoint means your alerts stop until someone ships a fix.
Chat apps work well too. A bot on the free Telegram Bot API can answer commands as well as send alerts, so typing /quote AAPL on your phone gets you a price. To share signals with a small group, Discord webhooks post to a channel in one request. Teams on Slack can do the same with Slack incoming webhooks.
Social data is noisier. The Stocktwits API gives you message streams and the bullish or bearish tags users put on their posts. It needs OAuth and the rate limits are tight, so confirm developer access is still open before you build on it. Reddit mentions are another signal, and the Reddit Data API can count tickers in r/stocks or r/wallstreetbets. Reddit changed its API pricing and terms in 2023, so read the current rules first, especially for commercial use.
If you already have a brokerage account, check its API before paying anyone else. Broker data is often the cheapest real-time feed you can get, and it can see your actual positions. Licensing is the limit. The data is usually for your personal use, so it can’t power a dashboard other people look at.
Signals off the Beaten Path: Alternative Data
One piece of advice holds for any build. Keep your data provider behind a single module in your code. Providers get renamed and sometimes shut down, as IEX Cloud users learned in 2024. With one module, a shutdown notice means editing one file. Without it, you’re rewriting the application.
Alternative data is anything outside prices and fundamentals. It’s where a home-built platform can show you something the big apps don’t, and also where quality varies most.
Through Quiver Quantitative you can pull congressional stock trades and corporate lobbying records over an API. Options traders tend to look at the paid Unusual Whales API, which tracks U.S. options flow and dark pool prints.
The Plumbing Nobody Talks About
Many developers use TradingView Lightweight Charts. It’s free and open source, and while it isn’t TradingView’s full charting product, it covers what most dashboards need. If you want indicators and range selectors built in, Highcharts Stock is the mature option, free for non-commercial use and licensed otherwise.
Start with the FRED API from the Federal Reserve Bank of St. Louis. One free key covers hundreds of thousands of series, Treasury yields and CPI among them. If you’d rather go to the agency that produces the numbers, the Bureau of Labor Statistics API has the jobs report and CPI series. For federal debt and Treasury rates, the U.S. Treasury Fiscal Data API needs no key at all.
Beyond Equities: Crypto and Currencies
Raw XBRL is awkward to work with, and that’s most of the reason people pay for fundamentals instead. Financial Modeling Prep and Finnhub, among others above, do the parsing for you.
Trading desks buy from a handful of institutional vendors on annual contracts. You won’t be one of their customers, but they set the standard everyone else is judged against.
Email suits the slower updates. For digests and earnings reminders, Twilio-owned SendGrid handles transactional email, and Postmark has a reputation for fast delivery, which matters if an email alert is time-sensitive.
How the Professionals Do It
Portfolios rarely stay all stocks. Several providers above handle crypto, but specialists are often cheaper.
After that, the usual move is to Twelve Data. Its free tier gives you delayed stock data with a bigger daily allowance, enough to refresh a watchlist a few times an hour, and indicators are built in there as well. Streaming is paid.
Two providers matter here. The first used to be Polygon.io and is now called Massive. Plenty of tutorials still use the old name, and the old api.polygon.io host still works. Massive is mostly about U.S. markets. Its free Stocks Basic plan allows five calls a minute and two years of history, which suits learning and end-of-day screens, while real-time trades and quotes start on the paid tiers.
Getting the Alert to You
Start with how fresh the data has to be. Exchanges charge for real-time prices and every reseller passes that fee on, which is why nearly all free tiers give you delayed or end-of-day data. For a daily summary, that’s fine. If you want an alert the moment a stock crosses a level, you’ll pay for real-time data or get it through a broker.
Most people’s first stock-data script calls Alpha Vantage, one of the oldest free stock APIs. Its useful trick is precomputed technical indicators, so you can ask for a moving average and get one back. The free allowance is 25 requests a day, though. That covers a tutorial but not a watchlist polled through a trading session.
Pick the channel by urgency. A broken price level deserves a push notification or a text. A daily summary can sit in your inbox.
For identity, Bloomberg runs OpenFIGI, a free API that maps tickers and other identifiers to one open standard, so each security keeps the same ID across your sources. For timing, the Python library exchange_calendars knows the holidays and session hours of exchanges worldwide. Massive and some other data APIs also have a market-status endpoint you can check before polling.
Drawing the Picture: Charting Libraries
The primary source is free. The SEC’s EDGAR APIs at data.sec.gov return every public company’s filing history as JSON with no key, along with financial-statement data pulled from XBRL. Two things trip people up. The endpoints don’t allow CORS, so call them from a server. The SEC also wants your app named in the User-Agent header, with requests kept under its published rate limit.
Research teams buy estimates and ownership data from FactSet, and company financials through Capital IQ from S&P Global Market Intelligence. For fund and ETF research, Morningstar licenses its ratings and analytics to businesses. Brokerages and fintechs are the main buyers of the cloud market data APIs sold by Xignite.
Before you choose: prices and free-tier limits in this market change often, and providers get bought or renamed. The specific limits here were checked in October 2026. Confirm the rest on each provider’s own pricing page, and read the redistribution terms if anyone besides you will see the data.
Keeping What You Collect: Time-Series Storage
Store what you fetch. It lets you backtest alert rules before trusting them, and you stop spending quota on data you already have. Market data is time-series data, and some databases are built for exactly that.
General charting libraries struggle with financial data. Candlesticks need special handling, and so do the gaps over nights and weekends when the market was shut.
Putting It Together
Currencies matter as soon as you hold a stock listed abroad. To convert a mixed portfolio into one currency, Open Exchange Rates covers more than 170 currencies with hourly updates on its free plan. For a daily rate at no cost, Frankfurter is an open-source API serving the European Central Bank’s reference rates.
The Free Weekend Build
- Prices: Massive Stocks Basic or Twelve Data
- Context: FRED and SEC EDGAR
- Storage: TimescaleDB
- Alerts: Telegram Bot API or ntfy
- Charts: TradingView Lightweight Charts
The Live Dashboard
- Prices: a paid Massive tier, Alpaca, or your broker’s API
- Fundamentals: Financial Modeling Prep
- News: Benzinga or Marketaux
- Storage: QuestDB or TimescaleDB
- Alerts: Pushover or Twilio, plus a SendGrid digest
Compiled October 2026. Inclusion isn’t an endorsement. Confirm pricing and data licensing on each provider’s site before you build on it.
With this many choices it’s easy to stall in research. To start, you need one data source, one database, one alert channel, and one chart library. Here are two starting points built from services in this guide.
