Every print in BigTape is Lit or Dark, and its color on the chart tells you where the trade happened. This guide explains both, and what each one lets you see.
Many places to trade one stock
A U.S. stock can trade in many places. There are more than a dozen public stock exchanges. There are also private trading venues, and brokers that fill orders themselves. Each venue sets its own fees and rules for matching orders. Trades are reported publicly wherever they happen.
A single order can even be split across several venues at the same moment. BigTape calls that a
BigTape sorts every print into one of two venue types. Lit means the trade happened on a public stock exchange, where waiting orders are on show. Dark means it happened anywhere else, off-exchange.
Lit prints
An exchange shows its waiting orders to the public. Anyone can see the best bid and the best offer, meaning the highest price someone will pay and the lowest price someone will accept, and how many shares wait at each. The best bid and the best offer across all exchanges together form the quote you see in most trading apps.
When a trade happens on an exchange, the report names the exchange. BigTape groups all of them under one label, Lit, because the exchange's order book is lit: on show before the trade. The opening and closing auctions also happen on exchanges, and their prints are Lit prints like any other.
On the chart, a Lit print is blue: a blue circle for a regular print, a blue diamond for a Sweep.
Dark prints
Off-exchange venues do not show their orders to the public before a trade. That is where the name Dark comes from. The word describes what is visible before a trade, and nothing more. Private venues like this are often called dark pools. Brokers and market makers that fill customer orders themselves also trade off-exchange, and many everyday orders from individual investors are filled this way.
Off-exchange trading is an ordinary part of the market. In recent years, by most published counts, close to half of U.S. stock volume has traded off-exchange. Dark prints come in every size, from a few shares to hundreds of millions of dollars. BigTape ranks them the same way it ranks Lit prints.
A Dark trade is reported publicly after it happens, just like an exchange trade. Regulators require off-exchange trades to be reported within 10 seconds of execution. The report shows that the trade happened off-exchange. It does not say which private venue or broker handled it.
On the chart, a Dark print is pink: a pink circle for a regular print, a pink diamond for a Sweep. The shape is the kind of trade and the color is where it traded, so a Lit print and a Dark print of the same kind share a shape. Every mark's tooltip and its name for screen readers also say Lit or Dark in words, so you never have to rely on color.
What you can and cannot see
For any print, Lit or Dark, you can see the price, the size, the time and the venue type. BigTape adds its rank against the ticker's own history. Both kinds of print can be large, and the rank works the same way for both.
You cannot see who traded. Neither kind of report names the firms or people involved. You cannot see the side, meaning which party started the trade. For a Dark print you also cannot see which venue handled it. You never see the orders that were waiting at a private venue before the trade.
Say two prints land a minute apart in the same stock. One is a $48M Lit print at $131.38. The other is a $52M Dark print at $131.40. You can compare their sizes, prices, times and ranks. You cannot tell who was behind either one, or whether the two are connected.
Some trades are reported late and out of order. A print's tooltip says
Over weeks and months, prints from every venue add up at certain prices. BigTape draws the heaviest of those price zones as