# Real-Time, Delayed and Historical Data > What real time market data really means, how it differs from delayed and snapshot data, where it comes from, what it costs and how to judge its quality. Source: https://learn.tradelabsai.com/programming/real-time-data/ Track: Programming and Data · Level: Intermediate · Updated: 2026-10-03 Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice. Cite as: TradeLabs Learn, "Real-Time, Delayed and Historical Data", https://learn.tradelabsai.com/programming/real-time-data/ Real time market data shows prices as trades and quotes happen, rather than minutes later. It sounds simple, but "real time" covers a wide range: a professional direct feed from an exchange arrives within microseconds, while a free web chart may refresh once a second from a consolidated source. For a long term investor, a short delay hardly matters. For a day trader or a bot reacting to price moves, data quality and speed directly affect results. Understanding where your data comes from helps you know what you can and cannot rely on. ## Types of market data delivery | Type | Description | Typical users | |---|---|---| | Delayed | Prices shown with a delay, often 15 minutes for exchange data | Casual investors, free sites | | Snapshot | Current price on request, not streamed | Occasional checks | | Real time streaming | Continuous updates as they happen | Active traders, bots | | Direct exchange feeds | Raw feeds straight from the venue | Professional and high frequency firms | | Consolidated feeds | Combined data from many venues | Brokers, retail platforms | ## Consolidated versus direct feeds In US stocks, trading happens on many exchanges. The Securities Information Processors (SIPs) combine their quotes and trades into a consolidated tape. Direct feeds from each exchange are faster because they skip the consolidation step, and professional firms often build their own view of the market from them. Retail platforms usually show consolidated or broker processed data. See [Exchanges](https://learn.tradelabsai.com/market-structure/exchanges/) and [Latency in Trading](https://learn.tradelabsai.com/orders/latency-in-trading/). ## Crypto data Each crypto exchange has its own order book and price, so "the price of Bitcoin" depends on the venue. Exchanges stream data free through WebSocket APIs. Index prices, such as those used for perpetual futures or settlement, are calculated from several exchanges. See [Mark Price vs Index Price](https://learn.tradelabsai.com/crypto/mark-price-vs-index-price/) and [WebSocket Market Data Streams](https://learn.tradelabsai.com/programming/websocket-market-data-streams/). On [TradeLabs AI](https://tradelabsai.com), the live charts use streaming exchange data. For Polymarket's crypto up or down rounds, it matters which source settles the market, because a different exchange's price can differ slightly at the deciding moment. See [Price to Beat and How Rounds Settle](https://learn.tradelabsai.com/prediction-markets/price-to-beat/). ## What real time data costs | Market | Typical cost model | |---|---| | US stocks | Exchange fees passed through brokers; non professional rates are much lower than professional | | Futures | Exchange fees per exchange group, monthly | | Forex | Usually broker quotes, no separate fee | | Crypto | Usually free from exchanges | See [Market Data Fees](https://learn.tradelabsai.com/orders/market-data-fees/). **Example: Measuring how stale your data is** A trader logs the exchange timestamp on each trade message alongside the time their program received it. Over an hour, the median difference is 45 milliseconds, but the 99th percentile is 900 milliseconds, mostly during a news spike. For a swing strategy, both numbers are irrelevant. For a bot placing orders on breakouts within a second, the slow tail means about 1 signal in 100 acts on prices nearly a second old. The trader moves the bot to a server closer to the exchange and keeps message handling light. See [Exchange vs Receive Timestamps and Latency Measurement](https://learn.tradelabsai.com/programming/latency-measurement/). ## Judging data quality | Question | Why it matters | |---|---| | Is it truly real time or delayed? | Delays hide the current market | | Which venues are included? | One venue may not reflect the whole market | | Are timestamps from the exchange or the receiver? | Determines how you measure delays | | How are outages handled? | Silent gaps cause bad decisions. See [Monitoring Positions, P&L and Risk](https://learn.tradelabsai.com/algo-trading/live-monitoring/) | | Does it include quotes or only trades? | Needed to model spreads | ## Practical tips - **Match data to strategy speed.** Slow strategies do not need expensive feeds. - **Use the same source live as in backtests,** or measure differences between them. - **Record your live data** for later replay and debugging. See [Market Data Replay](https://learn.tradelabsai.com/programming/market-data-replay/). - **Detect stale data** and stop trading on it. ## Frequently asked questions ### What is real time market data? Price and quote information delivered as trades and quote changes happen, rather than after a delay. ### Why is stock data delayed on free sites? Exchanges charge for real time data, so free services often show delayed prices, commonly 15 minutes behind. ### Is crypto market data free? Most crypto exchanges provide real time data free through their APIs, though professional data vendors charge for cleaned and combined datasets. Next, learn how to move data reliably from source to storage in [Data Pipelines and ETL](https://learn.tradelabsai.com/programming/data-pipelines-and-etl/). ## Continue learning - Next lesson: [Data Pipelines and ETL](https://learn.tradelabsai.com/programming/data-pipelines-and-etl/) - Previous lesson: [Tick Data and OHLCV Data](https://learn.tradelabsai.com/programming/tick-data-and-ohlcv-data/) - Related: [Tick Data and OHLCV Data](https://learn.tradelabsai.com/programming/tick-data-and-ohlcv-data/): Tick data records every trade or quote; OHLCV bars summarise them by time. Learn how bars are built, other bar types, storage costs and which data a strategy needs. - Related: [Market Data Explained](https://learn.tradelabsai.com/alternative-data/market-data-explained/): Market data covers trades, quotes, order book depth and reference data. Learn the main types, levels of data, real time vs delayed feeds, costs and common pitfalls. - Related: [Market Data Fees](https://learn.tradelabsai.com/orders/market-data-fees/): Real-time quotes and order book data often cost extra. Learn why exchanges charge for data, professional vs non-professional status and what data you actually need. - Related: [WebSocket Market Data Streams](https://learn.tradelabsai.com/programming/websocket-market-data-streams/): How WebSocket streams deliver live trades, quotes and order book updates. Learn subscriptions, heartbeats, reconnecting safely and handling gaps in Python. - Related: [Latency in Trading](https://learn.tradelabsai.com/orders/latency-in-trading/): Latency is the delay between a market event and your reaction to it. Learn the sources of trading latency, how it is measured and when it matters for your trades. - Related: [Monitoring Positions, P&L and Risk](https://learn.tradelabsai.com/algo-trading/live-monitoring/): Running algorithms need constant monitoring. Learn the key health, trading and risk metrics to track, how to design useful alerts and how to avoid alert fatigue.