Frankfurter vs Polygon.io
Category: Finance · Updated June 2026
Frankfurter has a more generous free tier (Unlimited, no key, no credit card) and requires no API key, making it the easier choice for getting started. Frankfurter currently leads on reliability with 98.87% uptime vs Polygon.io's 0% uptime over the last 30 days. Pick Frankfurter for hobby projects; consider Polygon.io if you need its specific feature set.
Side-by-side comparison
Frankfurter
Free currency exchange rates from the European Central Bank. No key required.
| Status | 🔴 Offline |
| 30-day uptime | 98.87% |
| Response time | 8619 ms |
| Free tier | Unlimited, no key, no credit card |
| Auth | No key required |
| Tier score | 1.0 — no friction |
Polygon.io
Real-time and historical stock, options, forex, and crypto market data with WebSocket streaming support.
| Status | 🔴 Offline |
| 30-day uptime | 0% |
| Response time | 694 ms |
| Free tier | Unlimited delayed data, free key, no credit card |
| Auth | API key |
| Tier score | 0.7 — free key, no card |
Which to choose?
- Pick Frankfurter if…you want zero friction — no account, no key, just call the endpoint. Also good if finance data without signup is a hard requirement.
- Pick Polygon.io if…its feature set (Unlimited delayed data, free key, no credit card) fits your request volume and you're comfortable with a free API key.
- Use both if…one goes down — they serve the same finance use case from different data sources, so you can implement a quick fallback.
Or use these alternatives
Other top-ranked Finance APIs you might consider:
- European Central Bank Rates — 🟢 Online · Unlimited, no key, no credit card
- Twelve Data — 🟢 Online · 800 calls/day, free key, no credit card
Frequently Asked Questions
Is Frankfurter or Polygon.io more reliable?
Based on our 30-day tracking, Frankfurter is more reliable with 98.87% uptime compared to Polygon.io's 0%. Both are measured from the same automated hourly checks — no self-reported data.
Which one has a more generous free tier — Frankfurter or Polygon.io?
Frankfurter has a more generous free tier. Its plan offers Unlimited, no key, no credit card vs Polygon.io's Unlimited delayed data, free key, no credit card. Frankfurter also requires no API key at all, making onboarding instant.
Can I use Frankfurter and Polygon.io together?
Yes, and it's straightforward. Frankfurter needs no key, while Polygon.io needs a free registration. You can use one as primary and the other as fallback without significant complexity.
What's the cheapest paid alternative if both Frankfurter and Polygon.io fail?
If you need a paid fallback, Open Exchange Rates is one of the more affordable options (from $12/mo). You can find the full list of paid alternatives on each API's detail page. Paid tiers typically offer SLA guarantees, higher rate limits, and dedicated support.
See full profiles: Frankfurter · Polygon.io · All Finance APIs