Large trades sometimes arrive in groups. Some land on several venues within a few thousandths of a second. Others gather in a tight price zone over minutes, or repeat one exact price. BigTape marks three kinds of groups so each one reads as a single event.
Sweeps
Market rules allow a special kind of order that can take shares from several venues at once. Each trade it creates carries a flag that says so.
BigTape groups flagged trades that land on two or more venues within 5 milliseconds into one
Venues report their parts separately. Without grouping, one Sweep would look like several unrelated trades. Say a Sweep takes $3.10M on one venue, $2.60M on a second, $2.00M on a third and $1.50M on a fourth, all within 5 milliseconds. BigTape shows one diamond for $9.20M.
A Sweep's label gives the spread and the total, for example “Sweep across 4 venues within 5 ms, $9.20M total. Side unknown.” On the chart, a Sweep is a diamond. Its size comes from the rank of its largest part. Hover over it and a thin line joins its parts.
A Sweep tells you someone wanted size quickly, across venues. It does not tell you which side, or why.
Block Bursts
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The box covers the time and price span of the group. Its label leads with the dollar total and the number of prints. The prints inside keep their own marks and ranks, so you can still see which one was largest. Only large prints count toward a Block Burst, so a run of small trades is never boxed.
A Block Burst says the trades happened close together. It does not say they were connected, who traded them or why. Block Bursts stay one click away, in the Standard and Everything layers.
Same-Price ×N
Picture five Dark prints at exactly $131.40, spread across an afternoon. BigTape draws a short solid bar at $131.40, from the first of those prints to the last, ending in a “×5” pill. A repeated exact price is easy to miss in a list of trades and easy to see as a bar. It tells you large Dark trades gathered at one price, not who traded them or why.
How the groups differ
A Sweep spans venues and lasts a few thousandths of a second. A Block Burst stays off-exchange and spans minutes, inside a tight price zone. Same-Price ×N stays off-exchange too, and repeats one exact price. Block Bursts and Same-Price ×N are built from Dark prints only. A Sweep is defined by its flag and its spread across venues.
A print can belong to more than one group. A Dark print inside a Block Burst can also be part of a Same-Price ×N set, and it keeps its own rank either way.
A fourth label is easy to confuse with these. A
Sweeps, Block Bursts and Same-Price bars appear in the Standard view and above. Recurring Blocks appear in Everything. The Simple view keeps the chart to prints and Dark Levels, so start there and add detail when you want it.