Polygon vs Alpha Vantage: Which Stock Data API Fits a Side-Project Budget

You want to build a stock screener. Maybe a magic-formula scan, maybe a custom backtest, maybe just a dashboard that pings the close of your watchlist every evening. You hit the data wall fast: free tiers from the big-name APIs come with throttles or restrictions that turn a weekend project into a debugging marathon.

The two most common entry points for developer-side stock data are Polygon.io and Alpha Vantage. They occupy slightly different positions — Polygon is the modern, well-funded data provider with fast-moving infrastructure; Alpha Vantage is the older, broader-coverage service that has been the default “free tier exists” answer since 2017. Which one fits depends almost entirely on what you’re building.

What you actually need from a stock data API

For most side projects, three things matter more than anything else:

1. What does the free tier let you do? A free tier that returns end-of-day OHLC for the full US universe is enough to run a magic-formula screen. A free tier rate-limited to 25 requests a day is not.
2. How wide is the coverage? Are you only looking at US stocks, or do you need options chains, forex, crypto, futures, or fundamentals?
3. Is the developer experience smooth? API key issuance, SDK quality, documentation freshness, response shape. The two providers are not equivalent here.

Latency, historical depth, and tick-level data also matter — but if you’re a side-project developer, you almost certainly don’t need microsecond-grade data. Daily or minute-level is plenty.

Pricing and free tiers at a glance

The shape below reflects each provider’s published tiers at the time of writing. Pricing pages change — verify before you commit.

The most important thing this table hides: Alpha Vantage’s free-tier limit dropped sharply over the last few years. If you’re following an older tutorial that assumes 500 requests a day, that’s no longer the deal. Polygon’s free tier, by contrast, is limited per-minute rather than per-day, which is more forgiving for development but less forgiving for a hosted job.

Coverage breakdown

US equities (the common case)

Both providers have full US equity coverage on paid tiers. On free tiers, both work — Polygon gives you per-minute throughput for fewer endpoints; Alpha Vantage gives you broader endpoints with a stricter daily cap.

Options

Polygon is the clearer pick on paid tiers. Full options chains, greeks, and historical option prices are available on their higher plans. Alpha Vantage exposes options data on its Premium plans, but the shape is less ergonomic for chain-walking.

Forex and crypto

Alpha Vantage gives you forex and crypto on the free tier, within the daily cap. Polygon requires the higher Stocks-plus-Currencies or Advanced plan. If your hobby project is a multi-asset dashboard, Alpha Vantage’s free tier is a real advantage here.

Fundamentals

Both expose basic fundamentals (income statement, balance sheet, cash flow). Polygon’s fundamentals data is generally newer and better structured. Alpha Vantage’s was the de facto standard for free fundamentals before SEC EDGAR’s API matured — today, EDGAR is often the better source for free fundamentals straight from filings.

Developer experience

Sign-up flow is similar: fill a form, get a key. The differences show up in everyday use.

• Polygon has typed SDKs in Python, Go, and JavaScript that map closely to the REST API. Docs render with example responses. WebSocket streaming is straightforward.
• Alpha Vantage has a thinner SDK story (the community Python package is the most-used). Docs are denser and older-looking. The CSV vs JSON toggle is per-endpoint, which surprises people.

If you’re prototyping and want to be reading clean JSON in your editor within five minutes, Polygon’s developer experience is noticeably ahead in 2026. If you’re already in a Python notebook with pandas-datareader set up, Alpha Vantage feels familiar.

Rate limits in practice

A side-project screener doesn’t need to hammer either API. But the shape of the limit affects how you structure your code:

• Polygon’s per-minute rate limit means a sleep-and-retry loop is fine. You can scan several thousand tickers overnight on the free tier if you’re patient.
• Alpha Vantage’s per-day limit makes the same scan impossible without a paid tier. Premium raises the cap by an order of magnitude or more.

When to pick which

• Polygon if: you want fast iteration on US equities or options, expect to graduate to a paid plan within a few weeks, and care about modern developer experience.
• Alpha Vantage if: you need forex or crypto on a free tier, you’re scripting in Python notebooks, or you only need a handful of end-of-day quotes per day and can live with the 25-call cap.

If you can’t decide, sign up for both — both keys are free, and running them side by side for a weekend will surface the friction points that actually matter to your project before you spend any money.

Honest caveats

Stock data APIs change pricing, restructure tiers, and tighten limits without much warning. The shape of this comparison should be stable for a year or two; the specific numbers may not be. Before you architect anything load-bearing on either provider, verify the current free-tier and paid-tier limits on their pricing pages, and budget for the price step-up if your project takes off.

And the usual reminder: better data does not become a trading edge by itself. The same close prices everyone has access to are still close prices everyone has access to.