The DOM shows you intentions: the resting orders waiting to trade. The tape — the time and sales window — shows you reality: every trade that has actually executed, printed one line at a time. If the order book is the menu, the tape is the receipt, and learning to read it is how you watch aggression happen tick by tick rather than infer it from a finished candle.
What the tape is
Time and sales, universally called the tape, is a scrolling list of completed trades in the order they happened. The name is a holdover from the ticker tape that printed quotes on paper ribbon a century ago; the function is unchanged. Every time a market order, or a marketable limit, hits a resting order, a trade prints to the tape. Unlike the DOM, which shows orders that may never execute, the tape shows only what did — it is the unarguable record of transactions. Reading it is the closest a trader gets to watching the raw auction unfold in real time.
Anatomy of a print
Each line on the tape carries a few fields: the time of the trade, often to the millisecond, the price it executed at, the size in shares or contracts, and usually a colour or flag indicating whether it hit the bid or lifted the ask. That last field is the crucial one for order flow. A trade that executes at the ask means an aggressive buyer reached up and took the offer; a trade at the bid means an aggressive seller pressed down and hit the bid. So each print does not just say a trade happened — it tells you which side was the aggressor, one transaction at a time.
Reading aggression through colour
Most platforms colour prints by aggressor side — conventionally green for trades at the ask and red for trades at the bid — so a fast eye can read the balance of aggression without reading numbers. A run of green prints climbing in price is aggressive buyers lifting successive offers; a cascade of red is sellers hitting successive bids. When the colour flips repeatedly at one price, buyers and sellers are fighting over a level. The tape thus turns the abstract idea of buying and selling pressure into something you can literally watch flicker by, and experienced tape readers feel the shift in tone before it shows on the chart.
Size and speed: the pace of the tape
Two things matter beyond colour: how big the prints are and how fast they arrive. Large prints reveal that size is trading — an institution, not just retail noise — and clusters of large prints at a level mark where real business is being done. The speed of the tape is its own signal: a tape that suddenly accelerates, prints flying past, shows a surge of activity that often accompanies a breakout or a flush, while a tape that goes quiet shows waning interest. Reading pace and size together, you can distinguish a genuine, well-supported push from a thin drift that will not hold.
The tape versus the DOM
The tape and the DOM are complementary halves of order flow, and the best readers watch both at once. The DOM shows resting liquidity — where orders are waiting — but those orders can be fake or pulled before they trade. The tape shows executed reality — trades that genuinely happened and cannot be un-printed. When the DOM shows a large offer and the tape shows that offer being repeatedly hit without price falling, you are watching absorption live: aggressive selling meeting a bigger passive buyer. Neither window tells the whole story alone; the DOM is intent and the tape is outcome, and the interplay between them is where the signal lives.
Absorption, exhaustion and the tape's limits
The most valuable tape reads are moments when aggression fails. Heavy one-sided prints that do not move price mean a large passive player is absorbing them, and when the aggressors give up, price often snaps the other way. A burst of frantic prints at the very end of a long move can mark exhaustion — the last participants piling in with no one left to continue. But the tape has real limitations: modern feeds are flooded with algorithmic and high-frequency prints that add noise, aggregated retail feeds may lump or delay trades, and spoofed orders never appear on the tape at all because they are cancelled before they trade. Read it as one high-resolution input, not an oracle, and always in the context of the DOM and the chart.