Support matrix

chartlet is before 1.0; screen reader and user testing are still pending. Statuses: Verified, Experimental (works, but may change between minor releases), Designed, not yet verified, Planned, Not supported.

Embedding

Context	Status	Notes
Standalone SVG	Verified	Byte-identical on macOS and Linux; covered by the golden-file tests.
HTML figure (caption, source, data table)	Verified	The data table is always present, in a native disclosure by default.
Astro component	Verified	Renders at build time and ships no chart JavaScript to the browser.
CLI and Rust API	Verified	The same renderer backs the CLI, the crate, and the npm package.
Mobile variant (mobile)	Verified	HTML profile: both variants in one wrapper, switched by a container query; the hidden one is display:none. Checked in Chromium at a narrow and a wide container, with zoom steps and series filter. Browsers without container queries keep the full-size chart.
<img src="chart.svg">	Designed, not yet verified	Title and description survive; the figure wrapper and data table do not apply.
Markdown	Planned	Not yet evaluated.
PDF and print (--variant print)	Verified	SVG with literal colors. Checked with resvg through Typst 0.15 (PNG and PDF) and with WebKit for bars, lines, a dark chart with declared colors, hatched bands, range bars, candlesticks, and a calendar heatmap. librsvg, Inkscape, Prince and wkhtmltopdf not yet tested.
E-mail clients	Planned	Not yet evaluated.

Browsers

Context	Status	Notes
Chromium (Chrome, Edge)	Verified	Automated accessibility scan (axe) and manual review during development.
Firefox	Planned	Standard SVG is expected to work. The Firefox build of Playwright did not start on the development machine, so the accessibility tree is not yet tested.
Safari (WebKit)	Verified for rendering	Checked 2026-10-12 with the WebKit build of Playwright (the engine of Safari, without Safari itself): all 76 example HTML profiles draw, every chart is a role="img" with a name and a description, the data table is present, the series filter hides series and the container query switches to the phone variant, with the same results as in Chromium. Not checked with VoiceOver.

Screen readers

Context	Status	Notes
VoiceOver (macOS)	Planned	The title and description are exposed as the accessible name and description; not yet tested.
NVDA (Windows)	Planned	Not yet tested.
JAWS (Windows)	Planned	Not yet tested.

Themes

Context	Status	Notes
Light (default)	Verified	The default palette keeps at least 4.5:1 contrast on white (lowest series color 5.17:1).
Dark	Verified	"theme": "dark" sets the palette through the same CSS custom properties and paints its own background. Lowest series color 7.65:1 against #0e131c.
Own colors (tokens, theme file)	Verified	Hex and rgb() values reach the stylesheet, the print and social variants and PNG. Pairs of colors that lie on top of each other are measured, and a ratio below WCAG 2.2’s is reported as low_contrast; other chart types’ scales are not measured. See Customize the look. Covered by unit tests.
Forced colours / high contrast	Planned	Planned; not yet shipped.
Host-page colors (var(--name) per layer)	Verified	A var() reference is passed through and falls back to the chart’s text color when the page defines nothing.

Time series

Context	Status	Notes
Calendar axis (ticks, timezone)	Verified	Ticks snap to calendar boundaries; a fixed UTC offset such as "+02:00" shifts the labels and the data table. Covered by unit and golden-file tests.
Line on the time axis	Verified	Up to six layers of 2000 observations per pane, at most four of the chart in palette colors; markers and value labels up to 60 observations per layer. The legend wraps into further rows.
Dense series	Verified	More observations than plot pixels is reported as dense_chart; measured at 131 KB of SVG for four layers of 2000 points and 196 KB for six.
Uncertainty band and modeled layers	Verified	lower/upper per point draw a band in the line’s color; "modeled": true dashes the line, hatches the band and says “modelled” in legend, description and table. Covered by unit and golden-file tests.
Reference lines (annotation)	Verified	Horizontal at value or vertical at time. A label that overlaps another annotation label, crosses a data line or leaves the plot is reported as label_overlap; it is not moved.
Zones (band)	Verified	A shaded range between bottom and top, from and to, or both, behind the data, with its label; described, no legend entry or table column. Covered by unit and golden-file tests.
Point markers (annotation with time and value)	Verified	Five shapes, a label beside the symbol that tries all four sides before label_overlap is reported, and a native tooltip. Zones, reference lines and markers share the limit of six per pane.
Small multiples	Verified	"type": "multiples": 2–12 panes with a shared value axis and one legend.
German texts and numbers ("locale": "de")	Verified	Every chart type.
area mark	Verified	Filled down to zero in the layer’s color; the value axis includes zero. Covered by unit and golden-file tests.
Line patterns and weights (dash, stroke)	Verified	solid, dashed, dotted; thin, regular, bold; the legend sample shows both.
Gaps (null) on a time chart	Verified	Break line, area and band; counted as missing in description and table. Also in small multiples.
Gaps in time (timeAxis.gaps: "collapse")	Verified	Every observed timestamp takes one evenly spaced slot, so weekends and holidays take no space; ticks sit on the first observation after each calendar boundary, annotations on the slot of an observation. Also in small multiples and zoom windows. Covered by unit and golden-file tests.
zoomSteps on a time chart	Verified	Windows by timestamp, HTML profile only; same radio-and-CSS mechanism as category zoom.
ohlc mark (candlesticks)	Verified	Wick from low to high, body from open to close; rising hollow, falling filled, in --chartlet-rise and --chartlet-fall. Beyond one candle per three plot pixels only the wicks are drawn and dense_chart is reported. Tooltips, table columns and description per candle layer. Covered by unit and golden-file tests.
Several panes on a time chart	Verified	Up to four panes stacked on one shared time axis, each with its own value axis and a share of the height by heightRatio; one legend with names unique across the chart. Covered by unit and golden-file tests.
zoomSteps on small multiples	Planned	Refused with option_not_supported.

Other chart types

Context	Status	Notes
Warming stripes, calendar heatmap	Verified	Shared diverging scale of 17 colors as CSS custom properties; covered by unit and golden-file tests.
Bars colored by group, small multiples of bars	Verified	group on data points (one color and legend entry per group, a Group column in the table) and multiples with categories and a values array and value axis per pane; covered by unit tests of validation, text and rendering and by golden-file tests, including the phone variant.
Box plots, error bars on bars	Verified	Quartiles by linear interpolation, whiskers within 1.5 boxes, outliers; unit tests of the statistics, validation, text and rendering in both orientations, and golden-file tests.
Forest plots, timelines	Verified	weight, summary and reference lines on range bars, and the timeline type with phases, milestones, markers, arrows and groups; unit tests of validation, text, arrows and rendering, and golden-file tests including the phone variant.
Waterfalls	Verified	Deltas, starts and totals with a check of the totals, both orientations; unit tests of the running total, text and validation, and golden-file tests including the phone variant.
Funnels and pyramids	Verified	Centered bars as wide as the values with the rate between stages, a pyramid with or without values, the warning for a widening funnel; unit tests of the rates, text and validation, and golden-file tests including the phone variant.
Radar charts	Verified	Axes with their own range or a grid-step default, grid rings with values, polygons told apart by dash pattern, strongest and weakest axis per series, warnings for many axes or series; unit tests of the ranges, text and validation, and golden-file tests including the phone variant.
Polar charts	Verified	Angle by category and linear radius from zero, wedges and lollipops, grid rings with values, names left out where they would overlap; unit tests of the geometry, text and validation, and golden-file tests including the phone variant.
Mosaic charts	Verified	Column widths by total, segment heights by share, colors by segment label across columns, shares written where they fit; unit tests of the sizes, text and validation, and golden-file tests including the phone variant.
Heatmaps	Verified	Sequential and diverging scales with text colors that keep 4.5:1, categories with fill and symbol, missing cells, ordering by label or value; unit tests of the cells, text, ordering and validation, and golden-file tests including the phone variant.
Cycle diagrams	Verified	Three to eight steps on a ring with the labels outside beside numbered dots or inside boxes, arrows along the ring, a hub with labelled links, roles and focus links; unit tests of the text and validation, a generated-specification test, and golden-file tests including the phone variant.
Layer stacks and nested scopes	Verified	Bands from the bottom up and frames inside each other, with items wrapped onto rows, notes at the side, roles and focus links; unit tests of the text, the geometry and validation, and golden-file tests including the phone variant.
Exploded layer stacks	Verified	Slabs in 2:1 dimetric projection from one projection function, lifted apart at equal gaps, guides, leader lines and the flat fallback on a compact canvas; unit tests of the gaps, the text and the fallback, and golden-file tests.
Plans	Verified	Rooms, buildings and open ground in 2:1 dimetric projection from one projection function, low walls, furniture, leader-line labels and phase patterns; unit tests of the projection, the text, the table and validation, and golden-file tests including the phone variant.
Architecture delta	Verified	Two views of a model side by side from one layout, so that components present in both keep their place, a ledger of added, removed, changed, moved and rewired with signs, and replaces for a component that stands in for another; unit tests of the ledger, the positions and validation, and golden-file tests.
Emphasis and legend strip	Verified	Up to two emphasized nodes and a path on flow, state, class, architecture, tree, network and sequence diagrams, drawn with a heavier outline and line as well as the accent, and a strip of node kinds, line patterns and emphasis below the drawing that wraps, grows the canvas and is left out in compact spacing; contrast of the tint and outline in every theme, unit tests of validation, texts, marks and legend, and golden-file tests including the phone variant.
Waffle charts	Verified	Apportioning of the squares (largest remainder, one square at least), the rest of a total, legend beside or below; unit tests of the squares, text and validation, and golden-file tests including the phone variant.
Venn diagrams	Verified	Two and three circles at fixed places, labels inside where they fit and on leader lines otherwise; unit tests of the layout, text and validation, and golden-file tests including the phone variant.
Value chain maps	Verified	Fixed positions, stage bands, dependencies, movement and inertia, labels placed beside dots where they cover nothing; unit tests of the layout, text and validation, and golden-file tests including the phone variant.
User journeys, service blueprints	Verified	Rows that no stage fills left out, the sentiment line with written values, the lines of interaction and visibility, and one block per stage on narrow canvases; unit tests of the layout, text and validation, and golden-file tests including the phone variant.
Story maps	Verified	Backbone, tasks and release slices with cut lines, and the list form on narrow canvases; unit tests of the layout, text and validation, and golden-file tests including the phone variant.
Kanban boards	Verified	Limits and the marks of a column over its limit, blocked cards, columns side by side or one under the other; unit tests of the layout, text and validation, and golden-file tests including the phone variant.
Fishbone diagrams	Verified	Bones alternating above and below the spine, two levels of causes, labels that wrap and never lean; unit tests of the geometry, text and validation, and golden-file tests including the phone variant.
Scatter plots	Verified	Groups, bubble sizes with a size legend, threshold lines, collision-free names, small dots and a limited table for many points; unit tests of the text, the table limit and validation, and golden-file tests including the phone variant.
Survival curves	Verified	Kaplan-Meier estimate with Greenwood confidence limits, censoring marks, number at risk; unit tests of the estimate, text and validation, and golden-file tests including the phone variant.
Regression, log axes, log-rank test, pinned Sankey nodes, nested treemaps, error bars on lines	Verified	Least squares on the logarithms for log axes, the Mantel-Cox test checked against an independent implementation, column_too_early, nested frames, line error bars; unit tests of each and golden-file tests including the phone variants.
Timeline summary phases and arrow routing, Sankey flows back	Verified	rollup weighted by length, arrows that turn beside bars in the way, loops for flows back; unit tests of each and golden-file tests.
Class and entity-relationship diagrams	Experimental	The layered layout of flow charts with class boxes and the marks of six relation kinds; unit tests of the text and validation and golden-file tests; like the flow chart it stands on, experimental.
Error bars on several series, timeline time zones	Verified	lower/upper on each series of grouped bars and lines with an interval column per series; a fixed-offset zone for timeline days, ticks and weekends; unit tests of both and golden-file tests including the phone variant.
Grouped box plots, shaded timeline weekends	Verified	Palette colors and a legend by group on boxes, violins and strips; Saturdays and Sundays as columns on axes of up to 120 days; unit tests of both and golden-file tests including the phone variant.
Mean marker, violin scales, hazard ratio, timeline progress and grouped rows, named scatter ticks and ranges	Verified	The hazard ratio checked against an independent implementation, shared densities for violin areas, row order by group; unit tests of each and golden-file tests including the phone variants.
Flow presets (PRISMA, Instanzenzug)	Experimental	Examples on the flow chart, which is itself experimental.
Violins and strips	Verified	Kernel density with Silverman’s bandwidth, fixed jitter; unit tests of both displays and validation, and golden-file tests including the phone variant.
Beeswarms and ridgelines	Verified	Dots placed from the lowest value on, each nearest the middle without touching another (checked for every pair); density curves on one shared scale; unit tests of both displays and validation, and golden-file tests including the phone variant.
Sankey diagrams	Verified	Columns by the longest path, barycenter ordering, bands with eased edges; unit tests of the text and validation, and golden-file tests including the phone variant.
Treemaps	Verified	Squarified rectangles with groups, labels where they fit, legend; unit tests of the layout text and validation, and golden-file tests including the phone variant.
Parliament charts	Verified	Seats in a semicircle with the number of rows chosen for the biggest dots, the line of the majority and a coalition; unit tests of the seats, text and validation, and golden-file tests including the phone variant.
Streamgraphs	Verified	Areas centered on a moving baseline with a scale bar for thickness and names in the middle of each band; unit tests of the baseline, text and validation, and golden-file tests including the phone variant.
Range bars	Verified	Vertical and horizontal, optional central value and hatched modeled ranges; dumbbells with values at both ends and ordering by change, covered by unit tests of layout, text and validation and golden-file tests including the phone variant.
Sequence and architecture diagrams	Verified	Laid out by chartlet; covered by unit tests of layout invariants (no overlapping boxes, main path straight, frames clear, no shortened names), and golden-file tests for portrait, landscape and the phone variant. Known limits: on a phone, five participants or a wide architecture still need 400–470 pixels (the canvas grows and says so); in landscape, edges that leave one component side by side keep their labels close to the component rather than on their own stretch.
Tree diagrams	Verified	Laid out by chartlet (subtrees pushed together, parents centered over their children, couples side by side); covered by unit tests of layout invariants (no overlapping boxes at 136 nodes with long names, parents centered, couples on one row, no shortened names) and golden-file tests for portrait, landscape and the phone variant.
Flow and state diagrams	Experimental	Laid out by chartlet on the same engine; covered by unit tests of layout invariants and golden-file tests. The layout may change between minor releases.
Diagram focus	Designed, not yet verified	Radio buttons and labels over the nodes, CSS :has(); checked with axe, not yet with screen readers.

Distribution and interactions

Context	Status	Notes
WebAssembly build in Node.js	Verified	The npm package renders through it by default; tests compare every example with the CLI output byte for byte on Node.js 22.
WebAssembly build in Cloudflare Workers	Verified	@casoon/chartlet/wasm with an imported chartlet.wasm; checked locally in workerd, not in a deployed Worker.
WebAssembly build in the browser	Designed, not yet verified	Same entry point; the playground compiles the module in a worker. Its first run on the deployed site is the verification; the browser versions it lists are derived from the features it uses, not tested one by one.
MCP server (@casoon/chartlet-mcp)	Designed, not yet verified	stdio server with chartlet_inspect_data, chartlet_validate_spec, chartlet_render, chartlet_explain, chartlet_inspect, chartlet_diagram_starter, chartlet_chart_starter, the schema as a resource and the MCP App view ui://chartlet/figure; covered by unit tests, an end-to-end test with the reference MCP client and a browser test of the view with axe, not yet tried in an MCP host such as Claude Desktop or Claude Code.
Native Node bindings	Not supported	The npm package renders through the WebAssembly build instead; CHARTLET_BIN selects the CLI.
Series filtering and stepped zoom	Designed, not yet verified	Available in the HTML profile with native controls and CSS; broader browser and assistive-technology verification is pending.
Mark tooltips	Designed, not yet verified	Native SVG titles provide hover hints; the description and table remain the accessible alternatives.

Versioning and compatibility

chartlet follows Semantic Versioning and is before 1.0, so the contract below is the one that applies to 0.x; the changelog lists every change by release.

One release, one version. The crate, the CLI, @casoon/chartlet and @casoon/chartlet-mcp of a release carry the same version number, and the schema in schema/ belongs to it. The packages do not need identical versions at run time: @casoon/chartlet-mcp depends on @casoon/chartlet with a caret range, which before 1.0 means the same minor (^0.23.0 accepts 0.23.x). Its bundled schema and the renderer are therefore always from the same minor, and a patch of the renderer never changes the specification.

Checked from the artifacts. Before a release, scripts/smoke-install.mjs packs both npm packages, installs the tarballs into an empty project outside the repository (no Rust toolchain, no CLI), and checks that a chart and a diagram render through WebAssembly, that the diagram equals its committed golden SVG, that chartlet.wasm, chartlet.css and the schema resolve from node_modules, that the manifest of a render names the installed compiler version and schemaVersion 1, that the schema bundled with chartlet-mcp is byte for byte the schema of the release, that the installed renderer satisfies the range chartlet-mcp declares, and that the MCP server lists its tools, renders a chart and a diagram and reports an invalid specification with code and path. After publishing, --published repeats this against the registry; --cli checks the cargo install --locked path. Experimental features are not part of the byte-stability promise between minors.

Compatibility of schema and renderer. chartlet-mcp validates nothing itself; the compiler does. Its bundled schema is a copy made at pack time and belongs to the release; the renderer it depends on is the same minor (caret range before 1.0), so every field the schema offers is one that renderer accepts, and a patch of the renderer does not change either. A different minor of the renderer under a newer chartlet-mcp is refused by npm’s range; forcing it is unsupported, because the schema may then offer or lack fields.

Reproducibility. A chart is a function of the compiler, the specification and the options that reach the renderer (format, variant, table, theme, view, perspective, idPrefix), plus the shipped stylesheet (chartlet.css, for styles: "external"). Pin the chartlet version exactly, keep the specification and options in version control, and --manifest records the version, specHash and outputHash to check it in CI (see Provenance).

Byte stability. Within a release, and across patch releases, the same compiler, specification and options give the same bytes, on macOS and Linux, through the CLI, the crate and the WebAssembly build alike; the golden-file tests (tests/golden.rs) enforce it. Between minor releases, output may change on purpose: layouts, spacing, text of descriptions, stylesheet details. Such changes are listed in the changelog, and the golden files of the new release show them. Re-render and review the diff when you move to a new minor; do not expect committed output to stay identical.

Supported runtimes.

Runtime	Supported
Node.js (@casoon/chartlet, @casoon/chartlet-mcp)	22.12 or newer (engines); the tests run on Node.js 22. No Rust toolchain is needed.
Rust (crate, CLI)	1.88 or newer (rust-version); development and CI use the version in rust-toolchain.toml.
Astro (@casoon/chartlet/astro)	6.0 or newer (optional peer dependency).
Cloudflare Workers, browsers	Through @casoon/chartlet/wasm; see the status in the Distribution table above.

Experimental features. Everything marked Experimental above (flow, state, class and entity-relationship diagrams and the flow presets) may change its specification or its layout in any minor release, and says so in the changelog.

Before 1.0. A minor release (0.23 to 0.24) may change the specification, remove a type or an option, and change output; a patch release (0.23.0 to 0.23.1) fixes defects only. Pin 0.23.x (~0.23.0, or an exact version for reproducible output) and move between minors deliberately. The schemaVersion of the specification stays 1 until a change cannot be expressed in it, and a different value is refused with unsupported_schema_version.

Migration policy. A change that makes a valid specification invalid is listed under Breaking in the changelog with what replaces it. A removed field or type is refused with invalid_spec and the JSON Pointer of the field, never silently ignored, so a failed render after an upgrade tells you where to look. Upgrade in this order:

1. Read the changelog entries between your version and the target, Breaking first.
2. Raise the pin of the packages (and the crate) together.
3. Render every specification (chartlet render, or renderChartDetailed in a script) and fix each invalid_spec at its path; add --strict to fail on warnings as well.
4. Re-render, review the output diff, and commit specifications and output together.

Example, from 0.20 to 0.21: 0.21.0 removed the experimental types topicmap and atlas. After npm install @casoon/chartlet@~0.21.0, a specification with "type": "topicmap" fails with invalid_spec at /type; remodel it as a network or tree diagram, then re-render. Every other specification renders as before, and committed output is expected to differ only where the changelog names a layout change.