QuantConnect

The QuantConnect data provider consolidates US Equity market data across all of the exchanges. Over-the-Counter (OTC) trades are excluded. The data is powered by the Securities Information Processor (SIP), so it has 100% market coverage. In contrast, free platforms that display data feeds like the Better Alternative Trading System (BATS) only have about 6-7% market coverage.

We provide live splits, dividends, and corporate actions for US companies. We deliver them to your algorithm before the trading day starts.

The QuantConnect data provider enables you to create a dynamic universe of US Equities.

Fundamental Universe

The live data for fundamental universe selection arrives at 6/7 AM Eastern Time (ET), so fundamental universe selection runs for live algorithms between 7 and 8 AM ET. This timing allows you to place trades before the market opens. Don't schedule anything for midnight because the universe selection data isn't ready yet.

// Run universe selection asynchronously to speed up your algorithm.
UniverseSettings.Asynchronous = true;
AddUniverse(SelectFundamental);

#  Run universe selection asynchronously to speed up your algorithm.
self.universe_settings.asynchronous = True
self.add_universe(self._select_fundamental)

ETF Constituent Universe

The QuantConnect data provider enables you to create a universe of securities to match the constituents of an ETF. For more information about ETF universes, see ETF Constituents Selection.

// Request an async universe of stocks that match the ETF constituents of SPY
UniverseSettings.Asynchronous = true;
var spy = AddEquity("SPY").Symbol;
AddUniverse(Universe.ETF(spy, UniverseSettings, ETFConstituentsFilter));

# Request an async universe of stocks that match the ETF constituents of SPY
self.universe_settings.asynchronous = True
spy = self.add_equity("SPY").symbol
self.add_universe(self.universe.etf(spy, self.universe_settings, self._etf_constituents_filter))

We aggregate ticks to build bars.

Discrepancies

In live trading, bars are built using the exchange timestamps with microsecond accuracy. This microsecond-by-microsecond processing of the ticks can mean that the individual bars between live trading and backtesting can have slightly different ticks. As a result, it's possible for a tick to be counted in different bars between backtesting and live trading, which can lead to bars having slightly different open, high, low, close, and volume values.

Opening and Closing Auctions

The opening and closing price of the day is set by very specific opening and closing auction ticks. When a stock like Apple is listed, it’s listed on Nasdaq. The open auction tick on Nasdaq is the price that’s used as the official open of the day. NYSE, BATS, and other exchanges also have opening auctions, but the only official opening price for Apple is the opening auction on the exchange where it was listed.

We set the opening and closing prices of the first and last bars of the day to the official auction prices. This process is used for second, minute, hour, and daily bars for the 9:30 AM and 4:30 PM Eastern Time (ET) prices. In contrast, other platforms might not be using the correct opening and closing prices.

The official auction prices are usually emitted 2-30 seconds after the market open and close. We do our best to use the official opening and closing prices in the bars we build, but the delay can be so large that there isn't enough time to update the opening and closing price of the bar before it's injected into your algorithms. For example, if you subscribe to second resolution data, we wait until the end of the second for the opening price but most second resolution data won’t get the official opening price. If you subscribe to minute resolution data, we wait until the end of the minute for the opening auction price. Most of the time, you’ll get the actual opening auction price with minute resolution data, but there are always exceptions. Nasdaq and NYSE can have delays in publishing the opening auction price, but we don’t have control over those issues and we have to emit the data on time so that you get the bar you are expecting.

Excluded Ticks

The bar-building process can exclude ticks. If a tick is excluded, its volume is aggregated in the bar but its price is not aggregated in the bar. Ticks are excluded if any of the following statements are true:

• The tick is suspicious.
• The tick is from the FINRA exchange and meets our price and volume thresholds.
• The trade has none of the following included TradeConditionFlags and at least one of the following excluded TradeConditionFlags:

TradeConditionFlags	Status	Description
RegularREGULAR	Included	A trade made without stated conditions is deemed the regular way for settlement on the third business day following the transaction date.
FormTFORM_T	Included	Trading in extended hours enables investors to react quickly to events that typically occur outside regular market hours, such as earnings reports. However, liquidity may be constrained during such Form T trading, resulting in wide bid-ask spreads.
CashCASH	Included	A transaction that requires delivery of securities and payment on the same day the trade takes place.
ExtendedHoursEXTENDED_HOURS	Included	Identifies a trade that was executed outside of regular primary market hours and is reported as an extended hours trade.
NextDayNEXT_DAY	Included	A transaction that requires the delivery of securities on the first business day following the trade date.
OfficialCloseOFFICIAL_CLOSE	Included	Indicates the "official" closing value determined by a Market Center. This transaction report will contain the market center generated closing price.
OfficialOpenOFFICIAL_OPEN	Included	Indicates the 'Official' open value as determined by a Market Center. This transaction report will contain the market center generated opening price.
ClosingPrintsCLOSING_PRINTS	Included	The transaction that constituted the trade-through was a single priced closing transaction by the Market Center.
OpeningPrintsOPENING_PRINTS	Included	The trade that constituted the trade-through was a single priced opening transaction by the Market Center.
IntermarketSweepINTERMARKET_SWEEP	Excluded	The transaction that constituted the trade-through was the execution of an order identified as an Intermarket Sweep Order.
TradeThroughExemptTRADE_THROUGH_EXEMPT	Excluded	Denotes whether or not a trade is exempt (Rule 611).
OddLotODD_LOT	Excluded	Denotes the trade is an odd lot less than a 100 shares.

• The quote has a size of less than 100 shares.
• The quote has none of the following included QuoteConditionFlags and at least one of the following excluded QuoteConditionFlags:
• The quote has one of the following QuoteConditionFlags:

QuoteConditionFlags	Status	Description
ClosingCLOSING	Included	Indicates that this quote was the last quote for a security for that Participant.
NewsDisseminationNEWS_DISSEMINATION	Included	Denotes a regulatory trading halt when relevant news influencing the security is being disseminated. Trading is suspended until the primary market determines that an adequate publication or disclosure of information has occurred.
NewsPendingNEWS_PENDING	Included	Denotes a regulatory Trading Halt due to an expected news announcement, which may influence the security. An Opening Delay or Trading Halt may be continued once the news has been disseminated.
TradingRangeIndicationTRADING_RANGE_INDICATION	Included	Denotes the probable trading range (Bid and Offer prices, no sizes) of a security that is not Opening Delayed or Trading Halted. The Trading Range Indication is used prior to or after the opening of a security.
OrderImbalanceORDER_IMBALANCE	Included	Denotes a non-regulatory halt condition where there is a significant imbalance of buy or sell orders.
ResumeRESUME	Included	Indicates that trading for a Participant is no longer suspended in a security that had been Opening Delayed or Trading Halted.
RegularREGULAR	Excluded	This condition is used for the majority of quotes to indicate a normal trading environment.
SlowSLOW	Excluded	This condition is used to indicate that the quote is a Slow Quote on both the bid and offer sides due to a Set Slow List that includes high price securities.
GapGAP	Excluded	While in this mode, auto-execution is not eligible, the quote is then considered manual and non-firm in the bid and offer, and either or both sides can be traded through as per Regulation NMS.
OpeningQuoteOPENING_QUOTE	Excluded	This condition can be disseminated to indicate that this quote was the opening quote for a security for that Participant.
FastTradingFAST_TRADING	Excluded	For extremely active periods of short duration. While in this mode, the UTP Participant will enter quotations on a best efforts basis.
ResumeRESUME	Excluded	Indicate that trading for a Participant is no longer suspended in a security which had been Opening Delayed or Trading Halted.

In the preceding tables, Participant refers to the entities on page 19 of the Consolidated Tape System Multicast Output Binary Specification.

Tick price data is raw and unfiltered, so it can contain a lot of noise. If a tick is not tradable, we flag it as suspicious. This process makes the bars a more realistic representation of what you could execute in live trading. If you use tick data, avoid using suspicious ticks in your algorithms as informative data points. We recommend only using tick data if you understand the risks and are able to perform your own tick filtering. Ticks are flagged as suspicious in the following situations:

• The tick occurs below the best bid or above the best ask


This image shows a tick that occurred above the best ask price of a security. The green line represents the best ask of the security, the blue line represents the best bid of the security, and the red dots represent trade ticks. The ticks between the best bid and ask occur from filling hidden orders. The tick that occurred above the best ask price is flagged as suspicious.

• The tick occurs far from the current market price


This image shows a tick that occurred far from the price of the security. The red dots represent trade ticks. The tick that occurred far from the market price is flagged as suspicious.

• The tick occurs on a dark pool
• The tick is rolled back
• The tick is reported late

Most live trading algorithms run on co-located servers racked in Equinix. Co-location reduces several factors that can interfere with your algorithm, including downtime from internet outages, equipment repairs, and natural disasters.

Live data takes time to travel from the source to your algorithm. The QuantConnect latencies vary depending on the data provider, but for US Equities, we have a latency of 5-40 milliseconds. A much more significant source of latency is the round trip order times from brokers, which can vary from 100ms to 5 seconds. QuantConnect is not intended for high-frequency trading, but we have integrations to high-speed brokers if you need.

When you request historical data or run warm-up, the amount of historical data you can access depends on the resolution of your data subscriptions. The following table shows the amount of trailing historical data you can access for each data resolution:

The QuantConnect data provider serves US Equities data for free.