missing-title
Warning. The title is empty or still the placeholder “Untitled chart”. The fix it suggests: state the decision or metric the reader should understand.
Free chart checker
Find the problem in your chart before your reader does
Paste a chart, get the rendered SVG, its alt text, and every structural QA finding with the fix ChartRelay suggests. The same review runs on every chart the API renders.
No sign-up and no API key. The public demo endpoint allows 30 checks a minute per IP address.
Try it
One chart in, one review out.
Describe the chart on the left and the review appears on the right: the rendered SVG, the alt text that ships with it, and each finding with its severity and suggested fix.
Describe the chart
No account and no API key. The chart is rendered and returned to you, not stored.
Or load an example
- Trips pie-too-many-slices.
- Trips too-many-series and dense-chart.
- Trips missing-title and long-labels.
Review
Run a check and the rendered SVG, its alt text, and every QA finding with its suggested fix appear here.
The rules
Exactly what the review looks for.
Eight rules, no scoring and no black box. When none of them fire, you get a single healthy result instead: no structural chart problems detected.
pie-multiple-series
Error. A pie chart was given more than one series, which it cannot compare clearly. It suggests a grouped bar chart, or keeping one series.
pie-too-many-slices
Warning. A pie has more than seven slices. It suggests keeping the largest six categories and grouping the rest as Other.
pie-negative-value
Error. A pie contains a negative value, which no slice can represent. It suggests a bar chart for signed values.
dense-chart
Warning. A non-pie chart carries more than 40 points in total, which will be cramped at that size. It suggests aggregating, filtering, or widening the output.
too-many-series
Warning. More than seven series ask the reader to track too many lines or bars at once. It suggests highlighting the important ones and muting the rest.
low-contrast
Warning. A colour that is actually drawn falls below 3:1 against the chart background — or, on a pie, the white percentage label falls below 3:1 against its slice.
long-labels
Tip. On a non-pie chart, a category label is longer than 12 characters, so the axis shortens it. It suggests shorter labels, or the full names in the subtitle. Pie slice labels are drawn in full, so this tip never fires on a pie.
How it works
From a one-off check to every chart you ship.
Describe the chart
Pick one of the five chart types, give it a title, and paste a category column plus one column per series. Or load an example that is built to fail.
Run the check
The page posts your spec to ChartRelay's public demo endpoint. It renders with the same engine the paid API uses, so the SVG and the findings are the ones you would get in production.
Read the findings
Every finding carries a severity, the rule that fired, what it saw, and a suggested fix. The alt text above them is the description a screen reader would announce.
Automate it
Renders from the API return the same findings on every call, so an agent or a build step can refuse a chart that comes back with an error instead of publishing it.
Questions
Before you paste anything.
Do I need an account?
No. This page calls ChartRelay's public demo endpoint, which takes no API key. It is rate limited to 30 requests a minute per IP address; if you hit that, wait a minute or create a free account and call the API directly.
What can it check?
Bar, line, area, pie and scatter charts, with up to 12 series and up to 100 points per series. This page renders at the default 900 × 520; the API accepts any size from 320 × 240 up to 2400 × 1600.
Will it tell me whether my numbers are right?
No, and nothing here should be read that way. The review only sees the chart specification you submit: its type, title, series and values. It cannot check your figures against a source, spot a bad join, or notice that a total is stale. Structure is all it judges.
Do I get a permanent link to the chart?
Not from this page. The demo endpoint renders your chart and returns the SVG in its response without storing the chart. Durable PNG and SVG URLs come from the authenticated API: POST /api/v1/charts stores the render and returns immutable /api/v1/charts/{id}?format=svg and ?format=png links that anyone can load.
Can an agent run the same review?
Yes. Every render from the API returns the same findings and the same alt text in its JSON response. The MCP server with its single render_chart tool ships in the repository's mcp/ directory; it is not published to npm yet, so today you run it from the repo.
Run this review on every chart, not just this one.
The API returns the SVG, durable PNG and SVG URLs, the alt text and these findings on every render — so a failing chart never reaches a reader.
Free plan: 1,000 renders a month, or 100 until you confirm your email address.