Why BigTape never says buy or sell

Some market tools tag large trades with a direction. BigTape never does. This guide explains why, and what you see instead.

Every trade has two sides

A trade needs a buyer and a seller. When 500,000 shares change hands, 500,000 shares are bought and 500,000 are sold. A $212 million print is $212 million bought and $212 million sold, at one price, in the same moment. Every print, of any size, has both sides.

So when people call a trade “a buy”, they mean something narrower. They mean the buyer started it by paying the price a seller was already asking. Traders call this the side of a trade.

The report does not say who started it

A public trade report lists the price, the number of shares, the time and whether the trade happened on an exchange or off one. It does not say which side started the trade. That is true for trades on exchanges and for trades off them. The venue that matched the trade knows which order arrived last, but that detail is not in the public report.

Some tools try to guess. A common method compares each trade's price with the best quotes at that moment. A trade at the asking price gets labeled buyer-started, and a trade at the bid gets labeled seller-started.

That guess has known gaps. Off-exchange trades are often priced between the best bid and the best offer, where the method has nothing to go on. Quotes in an active stock can change many times a second, so a small timing error can flip the label. A label that looks certain and is wrong is worse than an honest blank.

Even one large order can look mixed. It is often filled in many pieces over hours, and some of those pieces may be started by the other party.

Knowing the side would not explain the trade

Suppose a report did say who started a trade. You still would not know why it happened. A fund might be rebalancing. A dealer might be hedging an options position. A large order might be one slice of a plan that runs for weeks. The same print fits all of these stories, and many more. Each side of a print has its own reasons, and neither appears in the report.

Price is no shortcut either. If price rises after a large print, that does not show the print caused the rise. Prices change for many reasons at once, and many of them never appear on a chart.

What BigTape shows instead

BigTape sticks to what the report contains. Each print shows its dollar size, price, time, venue type and rank against the ticker's own history. Every Dark print carries the words “side unknown”. BigTape gives you the facts and leaves the judgment to you.

That still tells you a lot. Size and rank show how unusual a trade is for its ticker. Time and venue type show when and where it happened. The chart around it shows what price and volume were doing. Over time, you learn what is normal for the stocks you follow.

Prints never carry arrows. Exchange prints are solid blue discs and Dark prints are hollow pink rings, so shape and color both carry the venue. The up and down colors appear only on price candles, where they show whether a bar closed above or below its open. Prints never use them.

When you select a print, a panel called “Price after this print” shows what price did next. Its caption reads “Shown for context. A print does not cause or predict a price move.”

AI features follow the same rule. If you ask one about a trade's side, it replies, “BigTape can't tell buys from sells, so that part was left out.”