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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsChoose a market-data API by starting with the data your app must show or process—not a provider’s “real-time” label. Define the instruments, venues, freshness, history, expected users and use rights you need, then compare exact feeds and plans against those requirements. This guide focuses on U.S. equities; other asset classes and jurisdictions need separate confirmation.
Define the app’s data requirements first
Write down the requirements that could disqualify a provider before comparing features or prices. “U.S. stocks” or “real-time data” is not precise enough: feeds can cover different venues, have different delays and permit different uses.
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| Requirement | What to specify | Question to resolve with the provider |
|---|---|---|
| Instruments and geography | Equities, options or other asset classes; the symbols and markets; and the countries where the app will operate. | Which instruments, venues and regions are included in the exact feed and plan? |
| Coverage | Whether the app needs a particular exchange’s data, a venue-limited feed or consolidated U.S. market coverage. | Which exchanges contribute to the feed? Does “all U.S. stock exchanges” describe the actual entitlement being offered? |
| Freshness | Real-time, delayed, end-of-day or historical data, and the maximum delay your product can tolerate. | What is the stated delay for this feed, and does the app’s entitlement include it? |
| Data and delivery | Quotes, trades, bars, depth or options data; REST endpoints, WebSocket streams and historical access. | Which data types and delivery methods are available on the plan you would use? |
| Scale | Expected request rate, subscribed symbols, concurrent connections and peak usage; how much history the app needs. | What limits apply to requests, subscriptions, connections and historical queries? |
| Audience and use | Internal processing, personal display, customer display or redistribution; expected user types and launch markets. | Which agreements, subscriber classifications, entitlements, reporting and retention rules apply to this use? |
Record the exact feed, plan and entitlement next to every answer. A provider’s general product page or a feature available on another tier is not proof that your application can access it.
Match the feed and delivery model to the product
Make venue coverage explicit
Ask whether the feed is consolidated or limited to particular venues, and make sure the distinction is reflected in product language and user expectations. For example, Alpaca’s version 1.4.2 market-data documentation describes Basic equities coverage as IEX and Algo Trader Plus coverage as all U.S. stock exchanges. Those are plan details in that documentation, not an independent comparison or a permanent guarantee; check current coverage and entitlements directly with Alpaca. Alpaca’s market-data API documentation also distinguishes a Trading API for individuals using Alpaca’s platform from a Broker API for businesses building platforms on its infrastructure.
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Translate “real-time” into a stated delay
Ask the vendor to identify the feed by name and state its delay, rather than treating “real-time” as a universal category. Alpaca’s real-time stock-data documentation lists v2/delayed_sip as a 15-minute delayed SIP feed; that is the documented delay for that feed, not a general definition of near-real-time data. Check the feed documentation and your entitlement before relying on it for a product requirement.
Check the interfaces and limits your app will actually use
List the endpoints and streams needed by each user-facing feature. Confirm REST access, WebSocket delivery, history, request limits, symbols per subscription and concurrent streams for the specific plan. A provider may offer a capability somewhere in its product range without including it in the tier or entitlement you intend to purchase.
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Separate API access from permission to display or redistribute data
A working API connection does not by itself establish that an app may show the resulting data to customers or redistribute it. Classify every use in the product: internal or non-display processing, personal display, customer display, external redistribution, and any reporting or retention the agreements require. Then obtain written confirmation from the provider and the relevant exchange about the terms that apply to the actual feed, audience and distribution method.
NYSE requirements depend on the feed and use
NYSE says customers and vendors wishing to receive, use or redistribute its market data via an uncontrolled datafeed must submit required documentation. Its connectivity documents and pricing, contracts and policies provide materials to review. NYSE’s market-data pricing FAQ says external redistribution to non-employees can incur redistribution fees where applicable. These materials do not establish one universal rule or fee for every app; confirm whether the relevant policy applies to your feed and use.
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Nasdaq’s subscriber-agreement example is specific to its distribution context
Nasdaq Trader says firms distributing real-time Nasdaq data via controlled display devices must administer a Nasdaq Global Subscriber Agreement or equivalent to each end-user subscriber firm or individual. Review the applicable Nasdaq data-products agreements and forms and confirm whether your distribution arrangement falls within that stated context.
Include commercial terms in the product decision
Ask for the current written terms and a cost estimate that reflects the app’s audience and use—not just the technical subscription. Depending on the feed and arrangement, relevant costs or obligations may include the API subscription, exchange fees, user charges, redistribution fees, subscriber administration and reporting. Do not assume a personal or developer plan grants commercial, multi-user display rights.
Compare providers on evidence you can verify
| Provider documentation example | What it establishes | What still needs confirmation |
|---|---|---|
| Alpaca market-data documentation, v1.4.2 | It distinguishes Trading API access for individuals using Alpaca’s platform from Broker API access for businesses building on Alpaca’s infrastructure. It lists Basic and Algo Trader Plus and describes different equities coverage for those plans. | Current plan coverage, limits, prices, entitlements and commercial permissions. Treat the documented details as plan information, not an independent recommendation or permanent quote. |
| Alpaca real-time stock-data documentation | It describes WebSocket delivery and lists the named v2/delayed_sip feed as 15-minute delayed SIP. |
Which feed and entitlement suit the app, plus any current limits or permissions that apply. |
| Nasdaq Data Link API overview and Nasdaq Cloud Data Service API documentation | Nasdaq Data Link describes real-time, delayed and historical API options. | Which data product, agreement and price list apply. API availability alone does not establish a general redistribution license. |
For each candidate, ask vendors for written answers on coverage, feed delay, limits, usage rights and total cost. Compare any claims about latency under load, uptime or accuracy only when the provider supplies current commitments or evidence relevant to your own requirements; the cited product materials do not provide an independent cross-provider benchmark.
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- Write a requirements sheet. Specify instruments, exchanges, geography, freshness, history, delivery methods, scale and every intended data use.
- Remove mismatches. Exclude feeds that lack required venues or data types, exceed your acceptable delay, or cannot support your expected usage.
- Confirm the precise plan and entitlement. Get the feed name, included coverage and applicable limits in writing; do not infer them from a provider’s broader catalog.
- Clear display and redistribution rights. Describe who will see or process the data and how. Confirm the relevant agreements, subscriber obligations, reporting and fees with the provider and exchange as applicable.
- Compare total cost and operational fit. Include applicable subscription, venue, user and redistribution charges, then assess whether the documented interfaces and limits fit expected peak use.
- Validate claims that matter to the application. Ask for current commitments or evidence for reliability and performance requirements rather than treating feature descriptions as a benchmark.
Keep the resulting answers with the product’s data-source records. If coverage, audience, geography or data use changes, review the plan and agreements against the revised requirements.
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