The depth ladder is the most configuration-sensitive panel in the workspace. It updates faster than any chart, it aggregates resting liquidity into rows, and it exposes every display choice directly to the reader. A ladder that is configured carelessly will look busy while hiding the one thing it is good at: showing where liquidity sits relative to the last execution.
Ladder Anatomy
A depth ladder is a vertical column of levels centered on the last execution. Each level carries a bid quantity, an ask quantity, and often a traded-volume figure for the current session. The center line marks the spread. Above and below it, rows extend outward by a fixed number of ticks. The ladder does not show the whole book; it shows a window, and the window size is a setting that should match the instrument's typical depth rather than the panel's pixel height.
Column order is configurable, and the order matters more than it seems. Placing the traded-volume column between the bid and ask columns makes the ladder read as a single flow, while placing it at the outer edge turns the ladder into two separate lists. Neither is wrong, but switching between them mid-session is disorienting. Choose one arrangement per workspace and keep it.
Row Aggregation and Tick Grouping
Resting liquidity can be grouped so that each ladder row represents several ticks. Grouping reduces visual noise on instruments with dense books, but it also hides the exact level of a large order. A common compromise is to group the outer rows and leave the inner five ticks ungrouped. The ladder supports this through a display range rather than a single global multiplier, so the center of the book stays precise while the edges stay compact.
Grouping affects the highlight thresholds as well. A threshold expressed in contracts applies to the aggregated row, not to each underlying level. If a row sums five ticks, a threshold that looked reasonable at single-tick resolution will trigger far more often. Recalculate thresholds after changing the grouping, and note the grouping in the workspace description so the numbers remain interpretable.
Column Set and Highlight Rules
A ladder can display bid size, ask size, bid and ask counts, traded volume, delta at the level, and a session total. Each column adds information and cost. The most readable ladders use four columns or fewer: bid size, ask size, traded volume, and one derived measure. Additional columns are better placed in a separate panel where they can be read without competing with the ladder's vertical rhythm.
Highlight rules draw attention to unusually large resting size. They should be set relative to the instrument's own recent distribution, not to an absolute number copied from another market. A rule that fires on every row is decoration; a rule that fires a few times per session is a signal worth investigating. Review the rule after a week of sessions and adjust the multiplier rather than the absolute value.
Depth panels are sensitive to update frequency. If the ladder flickers or reorders rows constantly, reduce the update rate before changing any other setting. A calmer ladder is usually a more accurate one.
Execution Markers and Time Decay
Recent executions can be marked on the ladder and faded over a short interval. The fade is a display aid, not a data retention policy; the trades remain in the local store. A fade that is too fast makes the ladder feel empty between bursts, while a fade that is too slow accumulates markers until the ladder reads as a solid stripe. Two to five seconds is a practical starting range, adjusted to the instrument's activity.
Marker size and color should encode side, not magnitude. Magnitude is already visible in the traded-volume column, and encoding it twice produces a ladder that is hard to scan. Keep the marker small, use two colors, and let the numbers carry the size.
Ladder Behavior at the Edges
When the last execution approaches the top or bottom of the window, the ladder recenters. The recentering rule can be immediate or damped. Immediate recentering keeps the spread centered but makes the rows jump; damped recentering keeps the rows stable but lets the spread drift toward an edge. Neither behavior is universally better, and the choice should follow the way you read the panel: if you track individual levels, prefer damping; if you track the spread, prefer immediate recentering.
Some workspaces place two ladders side by side, one grouped and one precise. This is a legitimate use of screen space, but only if the two panels are linked to the same instrument and the same session. Unlinked ladders showing different sessions will disagree about traded volume at every level, and the disagreement is easy to mistake for a data fault.
Diagnosing a Ladder That Looks Wrong
- Rows appear duplicated. Check tick grouping and the instrument's tick size; a mismatch can map two ticks to one row.
- Quantities look too small. Check whether the feed reports size in contracts or in lots and whether a multiplier is applied.
- Markers stop appearing. Check the fade interval and whether replay is paused.
- Columns do not line up. Check the column order and whether a custom font is being substituted.
Each symptom has a single likely cause. Resist the urge to reset the workspace; a reset discards the evidence that would have told you which setting was wrong.