The short answer
Polygon.io and Alpaca differ on what free and real-time cost. Alpaca bundles a free real-time IEX feed at 200 requests/minute and charges $99/month for full SIP plus OPRA; Polygon.io is a standalone subscription with a free 15-minute-delayed tier and $199/month for full real-time SIP with unlimited calls (verified 2026-05-25). Alpaca wins if you trade there; Polygon as a broker-agnostic source.
Polygon.io and Alpaca are the two default US-equity market-data APIs for a retail AI stack, and they differ on what "free" and "real-time" cost: Alpaca bundles a free real-time IEX feed at 200 requests/minute and charges $99/month (Algo Trader Plus) for full SIP + OPRA, while Polygon.io is a standalone data subscription with a free 15-minute-delayed tier and $199/month (Stocks Advanced) for full real-time SIP with unlimited calls, both verified 2026-05-25. Alpaca wins on a free real-time-ish feed if you also trade there; Polygon wins as a broker-agnostic data source with unlimited-call flat pricing. Model both for your universe in the Data Vendor TCO.
TL;DR
| Dimension | Polygon.io | Alpaca |
|---|---|---|
| Free tier | 15-min delayed (Starter $29 entry) | free real-time IEX feed |
| Free-tier rate | 5 calls/min (Starter) | 200 requests/minute |
| Full real-time SIP | Stocks Advanced $199/mo | Algo Trader Plus $99/mo |
| Real-time rate | unlimited calls (Advanced) | 10,000 requests/minute (Plus) |
| Broker-agnostic | yes (data only) | tied to Alpaca brokerage |
| Options data | available on tiers | OPRA on Algo Trader Plus |
All figures verified 2026-05-25 against each vendor's official documentation. The per-vendor estimates at the foot are computed live from the shipped engine bundle.
The free tier is the first real difference
Alpaca's free tier includes a real-time IEX equities feed at 200 requests/minute, with the latest 15 minutes of historical data and 30 WebSocket equity symbols (verified 2026-05-25). It is genuinely real-time, just limited to IEX volume rather than the full consolidated SIP tape.
Polygon's free entry is 15-minute-delayed data; real-time requires a paid tier. Its Stocks Starter at $29/month is 15-minute delayed at 5 calls/minute; Developer at $79/month is delayed with unlimited calls; full real-time SIP arrives at Stocks Advanced $199/month with unlimited calls (verified 2026-05-25).
So for a free real-time-ish feed, Alpaca's IEX tier is the cheaper entry. For broker-agnostic data you do not have to trade through, Polygon is the natural source.
Full real-time: $99 vs $199, with a rate-vs-calls trade
Alpaca's Algo Trader Plus is $99/month and lifts you to full SIP across all US exchanges plus the OPRA options feed, with market-data rate raised to 10,000 requests/minute and unlimited WebSocket equity subscriptions (verified 2026-05-25).
Polygon's Stocks Advanced is $199/month for full real-time SIP with unlimited API calls (verified 2026-05-25). The headline split: Alpaca's full real-time tier is cheaper at $99 but capped at 10,000 calls/minute; Polygon's is $199 but advertises unlimited calls. For a workload that would brush a per-minute ceiling, Polygon's unlimited-call model removes that worry; for most retail workloads Alpaca's 10,000/minute is ample and $100/month cheaper.
Broker coupling is the structural choice
Alpaca's market data is part of the Alpaca brokerage account: the free IEX feed and Algo Trader Plus are the data side of a broker you also trade through. That bundling is the advantage if you trade on Alpaca anyway, and a constraint if you do not.
Polygon is data-only and broker-agnostic. You can pair it with any broker (IBKR, Schwab, Tradier) and keep data and execution separate. For a stack that wants its data source decoupled from its execution venue, Polygon is the cleaner fit.
How to choose
- Trading on Alpaca, want free real-time-ish data: Alpaca free IEX feed (200/min).
- Want full real-time SIP cheapest: Alpaca Algo Trader Plus ($99/mo, 10,000/min).
- Want unlimited-call flat pricing, broker-agnostic: Polygon Stocks Advanced ($199/mo).
- Prototyping, delayed data is fine, not on Alpaca: Polygon Starter ($29/mo, 15-min delayed).
- Decoupling data from execution venue: Polygon (data-only).
The decision reduces to "am I trading on Alpaca anyway (then its bundled data is cheapest), or do I want broker-agnostic data with unlimited calls (then Polygon)."
Connects to
- Polygon.io Pricing Plans 2026: the full Polygon flat ladder.
- Alpaca IEX vs SIP Free Tier 2026: the Alpaca data-feed deep dive.
- Intrinio vs Polygon.io 2026: Polygon against the institutional alternative.
- Data Vendor TCO: model the effective annual cost for your universe.
References
- Polygon.io / Massive. "Pricing." verified 2026-05-25 (Stocks Starter $29/mo 15-min delayed 5 calls/min, Developer $79/mo unlimited calls delayed, Advanced $199/mo full real-time SIP unlimited calls). https://polygon.io/pricing
- Alpaca. "About Market Data API." verified 2026-05-25 (free IEX feed 200 req/min, latest 15 min history, 30 WebSocket equity symbols; Algo Trader Plus $99/mo full SIP + OPRA, 10,000 req/min, unlimited WebSocket equities). https://docs.alpaca.markets/docs/about-market-data-api
Verified engine output
Show the recompute-verified inputs and outputs
| vendor_id | polygon |
|---|---|
| universe | medium |
| resolution | minute |
| needs_live | 1 |
| vendor › id | polygon |
|---|---|
| vendor › name | Polygon.io |
| vendor › url | https://polygon.io |
| vendor › short pitch | Flat-rate subscription. Real-time + historical for US equities. Popular retail default. |
| vendor › has overage | false |
| vendor › last checked | 2026-05-25 |
| vendor › tiers › row 1 › name | Stocks Starter |
| vendor › tiers › row 1 › monthly | 29 |
| vendor › tiers › row 1 › includes live | false |
| vendor › tiers › row 1 › includes options | false |
| vendor › tiers › row 1 › includes futures | false |
| vendor › tiers › row 1 › resolutions › row 1 | daily |
| vendor › tiers › row 1 › resolutions › row 2 | minute |
| vendor › tiers › row 1 › notes › row 1 | 15-min delayed market data |
| vendor › tiers › row 1 › notes › row 2 | 5 calls/min |
| vendor › tiers › row 2 › name | Stocks Developer |
| vendor › tiers › row 2 › monthly | 79 |
| vendor › tiers › row 2 › includes live | false |
| vendor › tiers › row 2 › includes options | false |
| vendor › tiers › row 2 › includes futures | false |
| vendor › tiers › row 2 › resolutions › row 1 | daily |
| vendor › tiers › row 2 › resolutions › row 2 | minute |
| vendor › tiers › row 2 › resolutions › row 3 | second |
| vendor › tiers › row 2 › notes › row 1 | 15-min delayed |
| vendor › tiers › row 2 › notes › row 2 | Unlimited API calls |
| vendor › tiers › row 3 › name | Stocks Advanced |
| vendor › tiers › row 3 › monthly | 199 |
| vendor › tiers › row 3 › includes live | true |
| vendor › tiers › row 3 › includes options | false |
| vendor › tiers › row 3 › includes futures | false |
| vendor › tiers › row 3 › resolutions › row 1 | daily |
| vendor › tiers › row 3 › resolutions › row 2 | minute |
| vendor › tiers › row 3 › resolutions › row 3 | second |
| vendor › tiers › row 3 › resolutions › row 4 | tick |
| vendor › tiers › row 3 › notes › row 1 | Full real-time |
| vendor › tiers › row 3 › notes › row 2 | Unlimited API calls |
| tier › name | Stocks Advanced |
| tier › monthly | 199 |
| tier › includes live | true |
| tier › includes options | false |
| tier › includes futures | false |
| tier › resolutions › row 1 | daily |
| tier › resolutions › row 2 | minute |
| tier › resolutions › row 3 | second |
| tier › resolutions › row 4 | tick |
| tier › notes › row 1 | Full real-time |
| tier › notes › row 2 | Unlimited API calls |
| monthly | 199 |
| one time | 0 |
| annual total | 2388 |
| meets resolution | true |
| meets live | true |
| meets options | true |
| meets futures | true |
| meets all | true |
Computed live at build time.
| vendor_id | alpaca |
|---|---|
| universe | medium |
| resolution | minute |
| needs_live | 1 |
| vendor › id | alpaca |
|---|---|
| vendor › name | Alpaca Markets |
| vendor › url | https://alpaca.markets |
| vendor › short pitch | Broker-bundled market data. Generous free tier via IEX feed; SIP feed requires paid plan. |
| vendor › has overage | false |
| vendor › last checked | 2026-05-25 |
| vendor › tiers › row 1 › name | Free (IEX feed) |
| vendor › tiers › row 1 › monthly | 0 |
| vendor › tiers › row 1 › includes live | true |
| vendor › tiers › row 1 › includes options | false |
| vendor › tiers › row 1 › includes futures | false |
| vendor › tiers › row 1 › resolutions › row 1 | daily |
| vendor › tiers › row 1 › resolutions › row 2 | minute |
| vendor › tiers › row 1 › notes › row 1 | IEX feed only (subset of volume) |
| vendor › tiers › row 1 › notes › row 2 | Free with Alpaca brokerage account |
| vendor › tiers › row 2 › name | Algo Trader Plus (SIP feed) |
| vendor › tiers › row 2 › monthly | 99 |
| vendor › tiers › row 2 › includes live | true |
| vendor › tiers › row 2 › includes options | true |
| vendor › tiers › row 2 › includes futures | false |
| vendor › tiers › row 2 › resolutions › row 1 | daily |
| vendor › tiers › row 2 › resolutions › row 2 | minute |
| vendor › tiers › row 2 › resolutions › row 3 | second |
| vendor › tiers › row 2 › resolutions › row 4 | tick |
| vendor › tiers › row 2 › notes › row 1 | Full SIP consolidated tape |
| vendor › tiers › row 2 › notes › row 2 | Options chains included |
| tier › name | Free (IEX feed) |
| tier › monthly | 0 |
| tier › includes live | true |
| tier › includes options | false |
| tier › includes futures | false |
| tier › resolutions › row 1 | daily |
| tier › resolutions › row 2 | minute |
| tier › notes › row 1 | IEX feed only (subset of volume) |
| tier › notes › row 2 | Free with Alpaca brokerage account |
| monthly | 0 |
| one time | 0 |
| annual total | 0 |
| meets resolution | true |
| meets live | true |
| meets options | true |
| meets futures | true |
| meets all | true |
Computed live at build time.
Frequently asked questions
- Polygon.io vs Alpaca market data: which is cheaper for real-time?
- Alpaca, for full real-time SIP: Algo Trader Plus is $99/month (10,000 requests/minute) versus Polygon's Stocks Advanced at $199/month (unlimited calls). Alpaca's free IEX feed is also real-time, limited to IEX volume (verified 2026-05-25).
- Does Alpaca have a free real-time feed?
- Yes. Alpaca's free tier includes a real-time IEX equities feed at 200 requests/minute with the latest 15 minutes of historical data. Full consolidated SIP requires the $99/month Algo Trader Plus tier (verified 2026-05-25).
- Is Polygon broker-agnostic?
- Yes. Polygon is a data-only API you can pair with any broker, keeping market data decoupled from your execution venue. Alpaca's market data is bundled with the Alpaca brokerage account (verified 2026-05-25).
- What is the rate-limit difference at the real-time tier?
- Alpaca Algo Trader Plus allows 10,000 requests/minute; Polygon Stocks Advanced advertises unlimited API calls. For workloads that would brush a per-minute ceiling, Polygon's unlimited model removes the concern (verified 2026-05-25).