> ## Documentation Index > Fetch the complete documentation index at: https://docs.marketlens.app/llms.txt > Use this file to discover all available pages before exploring further. # Classic Order Flow > Order book heatmaps and trades profiles on multi-exchange data. Order book **heatmaps** and **trades / volume profiles** are proven ways to read order flow. Most of them were built years ago for **one market at a time**, so multi-venue crypto needs care: how you **group** prices, how you **sum** venues, and what you can still tell apart per exchange. MarketLens keeps those classic tools and adapts them to **multi-market** selection. See also: [Unified order flow](/unified-order-flow), [L2 order book](/order-book). ## Heatmap Order book **heatmaps** were popularized by Bookmap around **2014–2016** and remain the standard way to see resting limit orders evolve through time: each column is a snapshot of the book, and color intensity marks larger size. Bookmap-style liquidity heatmap reference MarketLens extends that idea with **native multi-market** support. Below: an aggregated heatmap for BTC/USD **spot** across Binance, Bybit, Coinbase, OKX, Kraken, and Bitfinex. MarketLens aggregated multi-exchange order book heatmap Color intensity highlights interesting sizes. Settings (thresholds, scales, themes) help you focus on the liquidity that matters for your workflow. Heatmap intensity and display settings ### Price grouping Book data is first **bucketed** by a chosen price step into **non-overlapping** groups. Bids and asks use opposite edges so the spread stays clean: * **Bids** group **down** (toward lower prices) * **Asks** group **up** (toward higher prices) **Example** with a **\$10** step: several raw asks and bids collapse into a few cells (sizes add inside each cell). Heatmap price grouping: raw ladder on the left, grouped $10 cells on the right; bids group down, asks group up Each heatmap cell’s **vertical center** sits on the **price level** it represents (for example the 1230 and 1240 markers on the scale). Heatmap cell centers aligned to their price levels ### Multi-exchange aggregation After each venue is grouped the same way, the heatmap **always aggregates** across the selected exchanges. There is no per-venue layer in the heatmap: one cell, one value for the whole selection. Sizes are **signed**: **bids positive**, **asks negative**. Cells are summed with that sign: * Same side across venues **adds** (two bids in one cell → larger positive total) * Mixed sides **net out** (bid on one venue, ask on another in the same cell → a **bid/ask delta**, not two stacks drawn on top of each other) Multi-exchange heatmap aggregation with signed bid and ask sizes ## Trades profile **Volume profile** (total volume by price, without splitting buy and sell) was already common for years. MarketDelta’s Footprint® charts (around **2003**) popularized the next step: the same price ladder **inside each bar**, with **aggressive buys and sells** shown separately. Other platforms use other names for that idea. On MarketLens it is **trades profile**. Trades profile reference chart A **trades profile** shows **aggressive buy and sell volume at each price level inside a bar** — who hit the book, not who was resting (that is the heatmap). | Tool | What it shows | | - | - | | Heatmap | Resting limits over time | | Trades profile | Aggression inside the bar (buys vs sells at price) | | Volume profile | Total volume at price (buys + sells) | A core UI goal is to **read size without staring at digits**. Each price level is a horizontal bar whose **length is proportional to size** on a shared scale across the profile. Trades profile with bar length proportional to order size ### Display modes | Mode | What each level shows | | - | - | | **Trades profile** | Buys and sells **separately** | | **Delta** | **Buys − sells** (imbalance) | | **Volume profile** | **Buys + sells** (total volume) | | **Volume profile (delta)** | Same imbalance idea on a volume-profile layout | A **volume profile** is total size at each level (**buys + sells**), often drawn as bars from one side. **Delta** is **buys − sells** per level. Volume profile and delta modes Comparison of trades profile, delta, volume profile, and volume profile delta modes ### Price grouping Auction analysis **inside** candles needs **stable** buckets. Unlike the heatmap’s bid-down / ask-up edges, trades profile levels are **always grouped down** into **half-open** intervals so every trade lands in exactly one bucket (left edge **inclusive**, right edge **exclusive**). **Example** with a **\$10** step: a print at **1239.9** goes to the **1230** bucket; a print at **1240.0** goes to **1240**. Trades profile half-open price buckets grouped down ### Multi-exchange aggregation Trades profiles work on **executed volume** only (no signed bid/ask book cancellation). You can either: 1. **Aggregate** — sum size at each level (and each side, when buys and sells are separate) across the selected exchanges, or 2. **Show per exchange** — draw venues as separate bars/segments at the same levels. In the separate view, **hover** a venue to highlight only that exchange’s sizes so you can compare without leaving multi-market mode. ## References in product * [Unified order flow](/unified-order-flow) — limits and markets in one visual space * [L2 order book](/order-book) — live multi-market depth * [Tape](/tape) — aggressive prints as a visual stream This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.