DocsREST API

REST API v1

The API manages short charts, reports usage and signs URLs. It needs a verified email address and a paid plan (Starter or above). The machine-readable reference is openapi.yaml.

Base URL: https://app.renderchart.com/api/v1

Authentication

Send your secret key as a bearer token. Keep it on your server: anyone with it can sign URLs and change your charts.

curl https://app.renderchart.com/api/v1/usage \
  -H "Authorization: Bearer rc_sec_live_YOUR_SECRET"

Each key authenticates on its own. A rotated key keeps working for its grace period (24 hours by default); a revoked key stops at once.

Limits

120 requests a minute per key. Over that, requests get 429 rate_limited with a Retry-After header.

Errors

Every error has the same shape:

{"error": {"code": "plan_required", "message": "Editing a saved chart's data needs the Pro plan. On Starter, save a new short URL instead.", "plan": "pro", "feature": "live_short"}}

Status	Code	When
401	`unauthenticated`	The bearer token is missing or is not an active secret key.
403	`email_unverified`	The account has not verified its email address.
403	`plan_required`	The plan lacks the feature; `plan` names the cheapest plan that has it.
404	`not_found`	No such chart on this account, or no such route.
422	`validation_failed`	A field is invalid; `fields` lists messages by field. For chart parameters, `reason` carries the parser's code, such as `invalid_param:y`.
429	`rate_limited`	More than 120 requests in a minute.
503	`service_unavailable`	Charts are briefly unavailable; try again.

Short charts

A short chart saves chart parameters behind /s/{id}, which hides your key and data. See Short URLs.

curl https://app.renderchart.com/api/v1/charts \
  -H "Authorization: Bearer rc_sec_live_YOUR_SECRET" \
  -H "Content-Type: application/json" \
  -d '{"name": "Weekly signups", "params": {"type": "bar", "x": "Mon,Tue,Wed,Thu,Fri", "y": "12,19,3,5,2", "title": "Signups this week"}}'

The response includes the chart's url. params are the URL spec's parameters as strings; key, sig and exp are ignored and unknown parameters are dropped. Invalid parameters give 422 validation_failed.

Method and path	Does
`GET /charts`	Lists charts, newest first, 50 a page; pass `next_cursor` back as `cursor`.
`POST /charts`	Creates a chart.
`GET /charts/{id}`	Gets one chart, with its render count.
`PATCH /charts/{id}`	Renames it (`name`), or on Pro changes its data (`params`): the same URL then shows the new chart within about five minutes.
`DELETE /charts/{id}`	Deletes it; `/s/{id}` returns the 403 image within a minute.

Usage

GET /usage returns this month's unique renders against your monthly allowance. Cached charts never count. Free accounts' months are calendar months (UTC); paid months start on your billing day, on annual billing too.

{"period": {"start": "2026-10-01T00:00:00+00:00", "end": "2026-11-01T00:00:00+00:00"}, "plan": "starter", "limit": 10000, "used": 1204, "remaining": 8796, "blocked": false}

Signing

POST /sign signs a chart URL with the authenticating key's secret, so it renders without a watermark on paid plans. Send a url (a chart URL or a path with a query) or params, and optionally exp (Unix seconds) to make the URL expire.

curl https://app.renderchart.com/api/v1/sign \
  -H "Authorization: Bearer rc_sec_live_YOUR_SECRET" \
  -H "Content-Type: application/json" \
  -d '{"url": "https://c.renderchart.com/?type=bar&x=Mon,Tue&y=1,2"}'

You can also sign on your own server without calling the API: see Signing.

Public pricing

GET https://app.renderchart.com/api/public/pricing needs no key. It returns the plans on sale with their prices in US cents before tax, monthly allowances and features, and the founding offer with the spots left; openapi.yaml has the full shape. Any origin may read it, responses may be cached for five minutes, and each address may make 60 requests a minute (over that, 429 rate_limited).

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