Time & sales — reading the tape

If the order book is intent, the time & sales — the tape — is reality: a chronological print of every trade that actually executed, with price, size and time. "Reading the tape" (tape reading) is one of the oldest skills in markets, older than charts.

What each print tells you

• Price — where the trade happened.
• Size — how many contracts/lots changed hands in that print.
• Aggressor side (often colour-coded). A trade that executed at the ask was initiated by a buyer lifting the offer (aggressive buying); one at the bid was a seller hitting the bid (aggressive selling). This is how the tape reveals who is being aggressive.

What experienced tape readers look for

• Speed. A sudden burst of prints signals a surge of activity; a slow tape signals indecision or absence.
• Size clustering. Repeated large prints in one direction suggest a determined participant.
• Aggression at a level. Lots of trades hitting the bid into a support level, yet price not falling, is a clue (see absorption next).
• Large prints vs many small prints. One big print can be a single decisive player; a stream of uniform small prints can be an execution algorithm slicing a large order.

The honest limits

• The tape is fast and noisy. On liquid instruments it scrolls faster than any human can parse trade-by-trade; experienced readers watch rhythm and clusters, not individual lines.
• Availability again. True time & sales requires a central record of executions — present on exchange-traded markets, absent in spot forex, where your broker can only print its own fills.
• Aggressor classification is an inference, not a labelled fact, and venues vary in how they report it.