How to Read Trade Flow: Live Fills, Trading Value, and What Large Trades Can and Cannot Tell You

Quotes are intent, fills are outcome

If the order book shows orders still waiting, the trade list shows deals actually done, in time order. Each line records the time, price and size, and many screens also mark whether the trade came from the side that wanted to buy or the side that wanted to sell. Candles and volume bars on a chart are ultimately these fills bundled into fixed time units, so watching trade flow means looking at how a candle is built from the inside. Unlike quotes, fills are records that cannot be cancelled, so there is relatively little room for information that exists only for show, the way spoof orders do. That does not mean fills tell you the next move. A fill is something that already happened, and the screen does not show who made it or why. This article covers how to read trade flow and trading value next to the chart, and how far you can trust the large trades that catch the eye. Reading the volume bars themselves is covered separately in the article on volume analysis.

Definition and formulas: trade direction and trade strength

What moves price is the market order that immediately takes a resting limit order. So every fill has a side that took liquidity, the initiating side. When a buyer takes an order sitting at the ask, the fill is classed as buyer-initiated; when a seller takes an order sitting at the bid, it is seller-initiated. Crypto exchanges often include this flag in their trade data, and Korean brokerage screens also mark buys and sells in the trade list. The standard indicators built from it are trade strength and the taker buy ratio. On Korean brokerage screens, trade strength is commonly buyer-initiated volume divided by seller-initiated volume, times 100, so a value above 100 means buyer-initiated fills outnumbered the others in that window. The value changes a lot depending on the window summed, whether the day so far or the last so many trades, so check that first. Cumulative volume delta (CVD) keeps adding each candle's buyer-initiated volume minus seller-initiated volume and draws the running total as a line.

• Buyer-initiated fill: a trade that took an order resting at the ask
• Trade strength = buyer-initiated volume ÷ seller-initiated volume × 100
• Taker buy ratio = buyer-initiated volume ÷ total volume
• Cumulative delta = running sum of (buyer-initiated − seller-initiated) per candle

How to read it: see whether fills and price move together

Trade flow becomes useful when matched against price rather than read alone. If buyer-initiated fills increase as price clears resistance and candles close above it, that confirms, to that extent, that real trading came along with the breakout. The more telling scenes are when the two diverge. If seller-initiated fills keep pouring in but price barely falls, someone is steadily absorbing them with limit orders at that level; if buyer-initiated fills are heavy but price stays put, supply keeps arriving from above. Such absorption is a clue as to whether support and resistance are actually working. Look at trading value as well. If price moved a lot while trading value was smaller than usual, a few orders may have pushed through a thin book, and the move can be easily reversed. Conversely, if trading value rose to several times normal but price barely changed, treat it as a place where both sides clashed heavily and mark that level.

What large trades do tell you

A single line with an unusually large amount in the trade list draws the eye. Just as this site's whale trade report collects trades of 200,000 dollars or more by default, large trades are usually filtered by an amount threshold. What gives a large trade meaning is that, at that moment, a participant was urgent or confident enough to push that much size through at market in one go. In particular, if large trades print one after another in the same direction near an important chart level, such as long-standing resistance or the previous low, and price closes that way too, you can read it as the contest at that level tilting to one side, and no more. It is also worth checking whether, while large trades cluster on one side, their share of total trading value grows beyond usual. If the share is small, a few big lines are closer to noise; if it has grown, there is room to say large players drove that stretch. But that is the limit of what large trades can tell you, and the direction afterwards has to be checked separately, for the reasons in the next section.

The limits of large trades

Large trades hide more than you might think. First, there is no guarantee that one line is one person's decision. Big orders are usually split into small pieces and worked over time, so a truly large player's trading is often buried among small fills; conversely, several people's orders can be matched at the same moment and price and appear as one big line. Second, you cannot know the trade's purpose. Spot trades that hedge futures positions, trades chasing price gaps with other exchanges, and market orders sent by forced liquidation all print as large trades. A forced liquidation is not a decision but an order triggered because collateral ran out, so reading it as a large player's intent leads to the opposite interpretation. Third, there is another side. A large buyer-initiated fill also means a limit order sold the same size. Fourth, it is only one exchange's fill. At the same moment, a large trade in the opposite direction may have printed on another exchange or in the futures market. So a large trade is best treated not as a signal but as a reason to look at the chart around that time again.

Common misconceptions

First, the idea that price rises once trade strength is above 100. Trade strength records that buyer-initiated fills were heavier in the past window, and if enough limit sells absorb those buys, price does not rise. When the summed window is short, as early in the session, a few fills can swing the value widely. Second, the idea that a large buy fill means it is fine to follow. As the previous section showed, the purpose of that one line is unknown, and if same-side fills do not follow, it ends as a single event. Third, feeling that something big is happening the faster the trade list scrolls. Trading speed differs by time of day anyway, and a faster screen tells you only that volatility has risen. Fourth, assuming the direction flag is always accurate. In markets where the exchange does not provide the initiating side, tools estimate it by comparing with the prevailing quote, so fills in which pooled orders are matched at once, such as call auctions, are hard to assign. This is also why different tools show different trade strength for the same fills.

What looks different in crypto and stocks

Many crypto exchanges publish the initiating side of every fill in real time, so the taker buy ratio and cumulative delta can be calculated fairly accurately. On the other hand, the same coin trades simultaneously on many exchanges and in spot and futures markets, so one exchange's trade flow does not represent the whole. In futures markets, large one-sided fills often pour out during liquidation cascades. Korean brokerage screens show the trade list and trade strength in real time, and for Samsung Electronics or SK hynix many people also watch foreign and institutional intraday flows (preliminary figures). Call-auction fills at the open and close match pooled orders at once and print as one very large line, which should not be read as a large player buying or selling. US public trade data carries no initiating side, so estimation methods differ by tool, and large off-exchange trades are reported later and can slip into the trade list. Index products and large tech stocks trade so often that each line means even less.

• Crypto: each fill carries its side, but flow differs by exchange and market
• Crypto futures: large one-sided fills cluster during liquidation cascades
• Korean stocks: call-auction fills printing as one large line is normal
• US stocks: the initiating side is estimated, and off-exchange blocks slip in late

Reading it on a live chart

Trade flow is the fastest-moving information inside the candle still forming. If a few large buy fills print just after a one-minute candle opens, its trade strength and volume already look big, but it is common for opposing fills to follow before the candle ends and bring price back. So check the impression from fills against where that candle closed. If buyer-initiated fills were heavy but the candle closed leaving a long upper wick, someone absorbed the supply from above. If a tool shows the taker ratio or cumulative delta for the forming candle, remember that the value keeps changing until the candle closes. This is the same reason the site's volume spike scanner leaves the in-progress candle out of its multiple. Fills received over a WebSocket can be missed if the connection drops briefly, so after the screen has been open for a long time, keep in mind that running totals may have drifted from reality.

A practical checklist

Trade flow wobbles least when you anchor on chart levels and closed candles and read it on top of them. Check in this order, and if any item does not fit, give less weight to the impression from fills.

• Confirm which exchange and which market (spot or futures) the fills come from
• Confirm what window trade strength or the taker ratio sums
• Compare trading value with the same time of day on normal days
• See whether large trades came at an important chart level
• Sort out exceptional fills such as call auctions and forced liquidations
• Recheck the impression from fills against where the candle closed

Limits and disclaimer

Trade flow is a record of trades already made, so it does not tell you the next move. The purpose and identity behind a fill are invisible, it is the record of one exchange and one market, and the direction flag may be an estimate depending on the market. Expecting an outcome because of a large trade or high trade strength rests on weak ground, and using it with charts does not prevent losses. Fills are more trustworthy records than quotes, but interpreting them still has to rest on price, closed candles and a stop level set in advance. A fast-scrolling trade list in particular tends to rush decisions, so make a habit of checking the plan you made before looking at the screen. This article explains how fills and trading value work and does not recommend buying or selling any asset. Remember that trading decisions and responsibility for their results are your own.