Do I need an API key to render a chart?
No. GET /api/chart is open and rate limited by address at 60 origin requests a minute. A key is only needed for /api/v1/chart, which is private, uncached, and metered per key at 500 renders a UTC day.
A chart image API you can call with one GET request
Put the series in a query string, get a finished image back. PlotLark draws the chart on the server, so the result works in email, PDFs, bots, and plain image tags where a JavaScript charting library never runs.
- No client library
- SVG or PNG from the same URL
- Anonymous calls need no key
URL
https://www.plotlark.com/api/chart?type=bar&title=Tickets+closed+per+week&labels=W1%2CW2%2CW3%2CW4%2CW5%2CW6&values=34%2C41%2C38%2C55%2C61%2C74&width=900&height=520&color=%23ff7b5c&background=%23fffdf8&grid=true&valuesOn=truecURL
curl "https://www.plotlark.com/api/chart?type=bar&title=Tickets+closed+per+week&labels=W1%2CW2%2CW3%2CW4%2CW5%2CW6&values=34%2C41%2C38%2C55%2C61%2C74&width=900&height=520&color=%23ff7b5c&background=%23fffdf8&grid=true&valuesOn=true" --output chart.svgHTML
<img src="https://www.plotlark.com/api/chart?type=bar&title=Tickets+closed+per+week&labels=W1%2CW2%2CW3%2CW4%2CW5%2CW6&values=34%2C41%2C38%2C55%2C61%2C74&width=900&height=520&color=%23ff7b5c&background=%23fffdf8&grid=true&valuesOn=true" alt="Tickets closed per week" width="900" height="520" />No account and no key needed for these requests. Swap /api/chart for / to reopen the same configuration in the studio.
Every parameter the endpoint accepts
The whole chart lives in the query string. Anything you leave out falls back to the default in the last column.
| Parameter | Accepts | Default |
|---|---|---|
| type | bar, line, area, or donut | bar |
| title | Chart heading, up to 100 characters | Monthly progress |
| labels | Comma-separated labels, up to 36 characters each | Jan,Feb,Mar |
| values | Comma-separated non-negative numbers | 24,38,52 |
| width | 320–1600 pixels | 800 |
| height | 240–1200 pixels | 480 |
| color | Six-digit hex accent colour | #ff7b5c |
| background | Six-digit hex background colour | #ffffff |
| grid | Draw horizontal guide lines | true |
| valuesOn | Print the value beside each point | true |
| format | svg or png | svg |
Two endpoints, one grammar
Both endpoints read exactly the same parameters. They differ in who may call them and how the answer is cached.
- GET /api/chart
- Open to anyone, no key required, limited to 60 origin requests a minute per address. Responses are cached for five minutes and may be served stale for up to a day while they revalidate, so a popular embed mostly serves from the CDN.
- GET /api/v1/chart
- Authenticated with an Authorization: Bearer plk_… key from your account. 500 renders per UTC day and 120 a minute per key, answered with private, no-store and X-RateLimit-Limit / X-RateLimit-Remaining headers.
What comes back
- Content-Type
- image/svg+xml for the default response, image/png when you add format=png. PNG is rasterised on the server at exactly the width and height you asked for.
- Caching
- Public responses carry an ETag and Cache-Control: public, max-age=300, s-maxage=300, stale-while-revalidate=86400. A conditional request with If-None-Match gets a 304 instead of a redraw.
- Errors
- Invalid parameters return 400 with a JSON list of what to fix. Exceeding a limit returns 429. Nothing is drawn from a configuration the validator rejected.
What PlotLark does not do
These limits apply before you start, so nothing on this page promises more than the renderer delivers.
- One non-negative numeric series per chart, from 1 to 12 points.
- Bar, line, area, and donut. No stacked, dual-axis, or time-series grammar.
- 320–1600 px wide and 240–1200 px tall, on a solid six-digit hex background.
- Anonymous rendering is capped at 60 origin requests a minute per address.
Common questions
How much data can one chart hold?
One numeric series of 1 to 12 non-negative points, with labels up to 36 characters. Labels cannot contain commas, because commas separate the points in the query string.
Can I recover a key I did not copy?
No. Keys are shown once and stored only as a SHA-256 hash, so a lost key has to be revoked and replaced from the account library.