Alpaca's free market-data tier gives you the IEX feed only, which is a single exchange carrying roughly 3% of consolidated US equity volume, while the paid SIP feed (Algo Trader Plus, $99/month) gives the full consolidated tape across all US exchanges — both verified on 2026-05-2512. That distinction decides what the free tier is valid for: IEX is fine for research and prototyping but is not a complete picture of the market, so anything keying off NBBO-quality pricing for execution needs SIP. Here is exactly what each feed is and is not good for. Model the upgrade cost with the Data Vendor TCO.
TL;DR
- Free tier = IEX feed only, at 200 requests/minute1.
- IEX is one exchange carrying roughly 3% of consolidated US equity volume (3.2% overall as of Q4 2025)3.
- Paid SIP feed = Algo Trader Plus, $99/month, full consolidated tape across all US exchanges, 10,000 requests/minute1.
- IEX is valid for research, backtests, and prototyping. SIP is required for NBBO-quality execution pricing.
- Both feeds include 1-minute bars and trades; the difference is coverage breadth, not bar resolution.
IEX vs SIP at a glance
| Dimension | Free (IEX) | Algo Trader Plus (SIP) |
|---|---|---|
| Feed | IEX only (one exchange) | Full SIP consolidated tape |
| Volume coverage | ~3% of consolidated3 | ~100% (all US exchanges) |
| Monthly price | $0 | $991 |
| Rate limit | 200 req/min | 10,000 req/min1 |
| Valid for execution NBBO | No | Yes |
| Valid for research / backtests | Yes | Yes |
All values verified on 2026-05-2513.
What the IEX feed actually is
IEX (the Investors Exchange) is a single US equities venue. Alpaca's free tier streams IEX's own trades and quotes, not the consolidated market. IEX's share of total consolidated US equity volume is small — 3.2% overall as of Q4 2025 by IEX's own published statistics3. That means the free feed sees only the trades that printed on IEX and IEX's own best bid/offer, not the national best bid/offer (NBBO) formed across all venues.
For a developer, this has a precise consequence: prices on the free IEX feed are real, but partial. A quote may be stale or off-NBBO relative to the consolidated market because the other ~97% of volume is invisible to it.
What the SIP feed adds
The SIP (Securities Information Processor) consolidated tape aggregates trades and quotes from every US exchange into the official consolidated record, including the NBBO. Alpaca delivers SIP through the Algo Trader Plus subscription at $99/month, which also raises the market-data rate limit to 10,000 requests/minute1. This is the feed you need when a price drives an order, because it reflects the whole market, not one venue.
What each feed is valid for
Use the free IEX feed for:
- Learning the API and prototyping integration.
- Backtesting strategies where minor quote incompleteness is tolerable.
- Low-frequency research and screening on liquid names.
You need the paid SIP feed for:
- Any execution decision that keys off the current price (NBBO-sensitive entries/exits).
- Accurate spread and microstructure analysis.
- Real-time signals across a broad universe where venue coverage matters.
The honest rule: validate a strategy on the free IEX feed, then upgrade to SIP before risking real capital on live prices. The $99 step buys completeness, not just speed.
How it fits the rest of the stack
The IEX-vs-SIP split is Alpaca's version of a question every data-bundled broker faces: a free partial feed versus a paid complete one. For Alpaca's full rate-limit picture (trading and market data are separate ceilings), see Alpaca API Rate Limits 2026. For how Alpaca's bundled data compares to standalone vendors, run your universe through the Data Vendor TCO below — sometimes a dedicated vendor's flat tier beats $99 SIP, sometimes the broker bundle wins.
Verified figures
The free-tier IEX feed, the $99/month Algo Trader Plus SIP subscription, the rate limits, and IEX's ~3% consolidated-volume share were verified on 2026-05-25. Where Alpaca does not separately publish a per-feed historical-depth figure for the free tier, it is described rather than quoted.
Connects to
- Alpaca API Rate Limits 2026: the full trading + market-data limit picture.
- Cheapest Stock Market Data API 2026: where Alpaca's free feed ranks.
- Databento vs Polygon.io 2026: standalone vendors for deeper data.
- Data Vendor TCO: broker bundle versus standalone vendor cost.
References
Footnotes
-
Alpaca Markets. "About Market Data API" (free Basic = IEX feed, 200 req/min; Algo Trader Plus $99/mo, all US exchanges/SIP, 10,000 req/min). docs.alpaca.markets, verified 2026-05-25. https://docs.alpaca.markets/us/docs/about-market-data-api ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7
-
Alpaca Markets. "Real-time Market Data API." alpaca.markets/data, verified 2026-05-25. https://alpaca.markets/data ↩
-
IEX. "Equities market statistics" (IEX overall market share 3.2% as of Q4 2025). iex.io, verified 2026-05-25. https://www.iex.io/ ↩ ↩2 ↩3 ↩4
Verified engine output
Show the recompute-verified inputs and outputs
| 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
- What is the difference between Alpaca's IEX and SIP feeds?
- The free tier streams the IEX feed, a single exchange carrying roughly 3% of consolidated US equity volume. The paid SIP feed (Algo Trader Plus, $99/month) is the full consolidated tape across all US exchanges, including the NBBO.
- Is Alpaca's free market data tier good enough for trading?
- Not for execution. The free IEX feed is fine for research, backtesting, and prototyping, but it sees only IEX's slice of the market. Any decision that keys off the current NBBO price needs the paid SIP feed.
- How much does Alpaca's SIP feed cost?
- The SIP consolidated feed is part of Algo Trader Plus at $99/month, which also raises the market-data rate limit to 10,000 requests per minute.
- What share of US volume does IEX cover?
- IEX carried roughly 3.2% of consolidated US equity volume as of Q4 2025 by its own published statistics, so the free IEX feed is a small, partial view of the overall market.