Choosing a market data API looks like a pricing decision. It is really an engineering decision with a legal edge. A cheap feed that is unlicensed, drops ticks or cannot give you open interest will cost far more in rework than the subscription ever saved.
This checklist is ordered by how expensive each mistake is to fix later. Work through it with any vendor — including us.
1. Is the feed licensed for what you are doing?
Exchange data is not free to redistribute. In India, NSE, BSE and MCX license real-time data through authorised data vendors. If you are building anything customer-facing — an app, a dashboard, a signal service — ask the vendor for their exchange authorisation in writing, and whether your use (display, non-display, redistribution) is covered.
2–4. Coverage, depth and history
- Segments. Cash, index and stock futures, options, commodities, currency. Crypto and forex come from entirely different sources, so check each market separately.
- Depth. Last traded price is not enough for order-flow work. You need best bid/ask at minimum, and ideally market depth.
- History. How many years, at what granularity, and are expired F&O contracts included? Backtests on options need the contracts that no longer trade. (We go deeper on this in how much historical data a backtest really needs.)
The chart above is the hidden cost of multi-market coverage. A feed built for Indian cash hours is idle three-quarters of the week. A crypto feed has no maintenance window at all. Ask how the vendor handles restarts, and whether history is back-filled after an outage.
5–8. Quality, corrections and open interest
- Tick integrity. Are trades delivered in exchange sequence, with no gaps? Ask how they reconcile against the exchange’s end-of-day files.
- Corrections. Exchanges occasionally amend trades. Does the vendor push corrections, or leave bad prints in your history?
- Open interest. For F&O traders this is not optional. Price and volume cannot tell you whether positions were opened or closed — open interest can. Check whether OI arrives intraday or only at the close.
- Corporate actions. Splits, bonuses and dividends change historical prices. Without adjustment, every long-term backtest on equities is wrong.
9–12. Delivery, limits and cost
- Protocols. REST for history, WebSocket for streaming, and SDKs for the languages your team actually uses.
- Rate limits and symbol caps. A scanner watching 200 symbols needs very different limits from a single chart.
- Platform plug-ins. If you trade on NinjaTrader, AmiBroker, MultiCharts or Excel, a native connector saves you writing and maintaining a bridge. Pix Connect is one example that feeds all of these from one subscription.
- Total cost. Include exchange fees, per-segment charges and what happens when you add a second market.
Score your shortlist
Put every vendor you are considering into a simple matrix. Anything that fails a row in the top half should not make the final round, however cheap it is.
| Check | Weight | What “pass” looks like |
|---|---|---|
| Exchange licence | Critical | Written authorisation covering your use case |
| Segments & history | High | Every segment you trade, expired contracts included |
| Tick integrity | High | Documented reconciliation to exchange EOD files |
| Open interest | High for F&O | Intraday OI, not just end of day |
| Delivery | Medium | REST + WebSocket + your platform plug-in |
| Cost | Medium | Clear per-segment pricing with no surprise fees |
If your end goal is charting rather than code, you may not need an API at all. The Mirra indicators read the Accelpix feed directly inside NinjaTrader 8 — including open interest — so the data plumbing is already done.
Frequently asked
Do I need a licensed data vendor for personal trading?
For your own screen, your broker’s terminal data is usually enough. The moment you display data to others or build a product, you need a licensed source.
Is WebSocket always better than REST?
For live prices, yes. For history and one-off lookups, REST is simpler and cheaper to run.
Can one vendor cover stocks, crypto and forex?
Rarely in full. Crypto and forex come from different venues, so most teams combine an exchange-licensed Indian feed with separate crypto and forex sources.
- NSE, BSE and MCX publish their lists of authorised data vendors on their websites.
- Accelpix Pix API and Pix Connect product pages, accelpix.com.
Educational content only — not investment advice. Trading in securities, derivatives, crypto and forex involves substantial risk of loss.