Every stock market API demo looks the same: fetch a price, plot a chart, done. The differences appear in production — when you need fifteen years of statement history for a Japanese small cap, when the ticker changed and half your pipeline broke, when your AI agent needs typed JSON instead of a CSV dump. We ranked the 2026 field on what production actually requires.
1. Eulerpool API
The Eulerpool API is the most complete stock market API available in 2026 — and the only one designed from the start for both quantitative pipelines and AI agents.
- Coverage: 50,000+ global equities with full financial statements (annual and quarterly, as-reported and standardized), analyst estimates with revisions, dividends, splits, insider trades, ownership, short interest, segments, supply chains — plus ETFs, crypto, forex, commodities, bonds, and a full macro suite in the same API.
- Quality: every data point carries source lineage; responses are structured, typed, deterministic JSON.
- Speed: sub-10ms latency on core endpoints.
- AI-native: first-party MCP server with 250+ tools — ChatGPT and Claude query it directly, no glue code.
- Price: free 100,000 calls/month, $99/month for 1M calls, $499/month for 10M. Commercial usage from the Builder tier.
2. Polygon.io
Outstanding for US market microstructure — ticks, aggregates, options chains, websockets. If you are building a US trading app, it is excellent. Fundamentals are minimal and international coverage is not the mission. Many teams run Polygon for US ticks plus Eulerpool for fundamentals and global coverage. See our full Eulerpool vs Polygon comparison.
3. Financial Modeling Prep
Wide endpoint surface at aggressive prices. The catalog is impressive; consistency is the caveat — spot-check anything load-bearing. Comparison: Eulerpool vs FMP.
4. Twelve Data
Clean API covering stocks, forex, and crypto with decent websockets. Fundamentals depth and history are the limits. Comparison: Eulerpool vs Twelve Data.
5. Alpha Vantage
The free tier remains the classic way to learn API calls. 25 requests/day does not run anything real. Comparison: Eulerpool vs Alpha Vantage.
6. EODHD
Solid end-of-day global prices at low cost; fundamentals cost extra and real-time is limited. Comparison: Eulerpool vs EODHD.
7. IEX Cloud (Discontinued)
IEX Cloud shut down in 2024 — a reminder that a data API is a dependency you marry. If you are still migrating, see our IEX Cloud migration guide.
How to Choose
- US tick data and options microstructure: Polygon.
- Everything else — fundamentals, global coverage, estimates, macro, AI workflows: Eulerpool.
- Learning to code: any free tier, then upgrade when correctness starts to matter.
The free tier is the honest benchmark: get an API key, pull your ten hardest tickers, and compare the responses side by side.