Style Guide

All style fields live inside the "style" object at the top level of your JSON file. Every field is optional — the defaults produce a clean, publication-ready chart with no configuration needed.

{
  "style": {
    "major_tick": "year",
    "minor_tick": "quarter",
    "font_size": 11
  },
  "tasks": [ "..." ]
}

All fields at a glance

Field	Category	Default	Purpose
width	Layout	14.0	Figure width in inches
row_height	Layout	0.3	Row height in inches
bar_height	Layout	0.5	Bar height as fraction of row height
label_fraction	Layout	0.0	Label panel width (0 = auto)
indent_size	Layout	3	Spaces added per nesting depth
font_size	Typography	12.0	Base font size in points
bold_tasks	Typography	true	Auto-bold top-level task labels
number_tasks	Typography	true	Prefix labels with hierarchy numbers
background	Colors	"#FFFFFF"	Figure background color
grid_color	Colors	"#E0E0E0"	Vertical gridline color
row_band_color	Colors	"#F5F5F5"	Alternating row band fill
colors	Colors	10-color palette	Auto-cycle colors for top-level tasks
subtask_lightening_pct	Colors	0.0	Lighten child colors per depth level (%)
milestone_color	Milestones	"#FFD700"	Default milestone marker color
milestone_marker	Milestones	"D"	Default milestone marker symbol
milestone_size	Milestones	14.0	Default milestone marker size (pts)
major_tick	Ticks	null	Major tick interval (year/quarter/month/week/day)
minor_tick	Ticks	null	Minor tick interval (year/quarter/month/week/day)
major_grid_width	Ticks	2.0	Major gridline linewidth
minor_grid_width	Ticks	1.5	Minor gridline linewidth
tick_position	Ticks	"top"	Tick label position: top / bottom / both
table_colorize	Table	true	Show color accent gutter in table output
table_show_markers	Table	true	Draw milestone markers in table output
table_columns	Table	[]	Custom ordered column definitions

Layout

Field	Default	Description
width	14.0	Figure width in inches. Increase for wide date ranges or many columns.
row_height	0.3	Height of each row in inches. Lower values produce a more compact chart.
bar_height	0.5	Bar height as a fraction of row_height. 0.5 means the bar occupies half the row.
label_fraction	0.0	Width of the task label panel as a fraction of the total figure width. 0.0 (default) auto-sizes the panel to fit the longest label.
indent_size	3	Number of extra space characters added per nesting depth in the label panel.

Typography

Field	Default	Description
font_size	12.0	Base font size in points, applied to both task labels and tick labels.
bold_tasks	true	When true, depth-0 (top-level) task labels are automatically rendered in bold. Individual tasks can override this with the bold field.
number_tasks	true	Prefix task labels with hierarchical numbers (1, 1.1, 1.1.1, …).

Colors

Field	Default	Description
background	"#FFFFFF"	Figure and axes background color.
grid_color	"#E0E0E0"	Color of all vertical gridlines.
row_band_color	"#F5F5F5"	Alternating row band fill color (every other row is tinted). Also used as the label panel background tint.
colors	see below	Ordered list of hex colors automatically cycled across top-level tasks that have no explicit color. The default palette is 10 colors (steel blue, orange, green, coral, sky blue, amber, purple, cyan, hot pink, emerald).
subtask_lightening_pct	0.0	Percentage to lighten a child task’s inherited parent color per depth step. 25 means each level is 25% lighter. Set to 0 to disable.

Milestones

Field	Default	Description
milestone_color	"#FFD700"	Default fill color for milestone markers when no task-level color is set.
milestone_marker	"D"	Default matplotlib marker symbol for milestones. Common options: "D" (diamond), "*" (star), "^" (triangle), "o" (circle), "s" (square).
milestone_size	14.0	Default marker size in points. Override per-task with marker_size.

Tick marks and gridlines

jsonantt draws two levels of tick marks: a major level (prominent gridlines, bold labels) and a minor level (lighter gridlines, no labels).

Field	Default	Description
major_tick	null	Major tick interval. One of "year", "quarter", "month", "week", or "day". null disables major ticks.
minor_tick	null	Minor tick interval. Same values as major_tick. Typically set to a finer interval than major_tick.
major_grid_width	2.0	Linewidth of major gridlines.
minor_grid_width	1.5	Linewidth of minor gridlines.
tick_position	"top"	Where to draw the x-axis tick labels. Options: "top", "bottom", or "both".

Typical tick combinations:

major_tick	minor_tick	Best for
"year"	"quarter"	Multi-year roadmaps
"quarter"	"month"	1–2 year plans
"month"	"week"	Quarterly sprints
"week"	"day"	Short-horizon detail

Table output

These fields only affect -t / --table output.

Field	Default	Description
table_colorize	true	Show task bar colors as an accent gutter in the table.
table_show_markers	true	Draw milestone diamond markers in the table output.
table_columns	[]	Ordered list of column definition objects. Empty list uses the default column set. See sub-table below.

table_columns column definition object

Each entry in table_columns is an object with the following fields:

Field	Type	Default	Description
field	string	required	The data key to display. Built-in values: name, start, end, duration. Any custom key stored on a task (e.g. cost, owner) works too.
label	string	same as field	Column header text.
width	number	auto	Column width in pixels.
align	string	"left"	Text alignment: "left", "center", or "right".

{
  "style": {
    "table_columns": [
      { "field": "name",  "label": "Task",       "width": 220 },
      { "field": "start", "label": "Start",      "width": 100, "align": "center" },
      { "field": "end",   "label": "End",        "width": 100, "align": "center" },
      { "field": "owner", "label": "Owner",      "width": 120 },
      { "field": "cost",  "label": "Budget ($)", "width": 100, "align": "right" }
    ]
  }
}

Full style example

This is the style block from the bundled complex.json example:

{
  "style": {
    "row_height": 0.3,
    "font_size": 12,
    "indent_size": 3,
    "subtask_lightening_pct": 25,
    "major_tick": "year",
    "minor_tick": "quarter",
    "tick_position": "both"
  }
}

And a maximally-configured reference block showing every field:

{
  "style": {
    "width": 16.0,
    "row_height": 0.28,
    "bar_height": 0.5,
    "font_size": 11.0,
    "indent_size": 3,
    "label_fraction": 0.0,
    "subtask_lightening_pct": 20,
    "background": "#FFFFFF",
    "grid_color": "#E0E0E0",
    "row_band_color": "#F5F5F5",
    "milestone_color": "#FFD700",
    "milestone_marker": "D",
    "milestone_size": 14.0,
    "major_tick": "year",
    "minor_tick": "quarter",
    "major_grid_width": 2.0,
    "minor_grid_width": 1.5,
    "tick_position": "top",
    "bold_tasks": true,
    "number_tasks": true,
    "table_colorize": true,
    "table_show_markers": true
  }
}