Documentation

Render anything in three calls.

Authenticate with a key, then send a URL or HTML. Every endpoint returns the file directly — no polling, no webhooks, no SDK to install.

Quickstart

Create a free key (email-verified, 500 renders a month, no card), then make your first call. The response body is the image.

# a full-page screenshot, saved as PNG
curl -X POST https://renderkit.keelhelm.com/v1/screenshot \
  -H "Authorization: Bearer sk_your_key" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com","full_page":true}' \
  --output shot.png

// app/api/shot/route.ts — Next.js route handler
export async function GET() {
  const r = await fetch("https://renderkit.keelhelm.com/v1/screenshot", {
    method: "POST",
    headers: { Authorization: `Bearer ${process.env.RENDERKIT_KEY}`, "Content-Type": "application/json" },
    body: JSON.stringify({ url: "https://example.com" }),
  });
  return new Response(r.body, { headers: { "Content-Type": "image/png" } });
}

// src/pages/shot.png.ts — Astro endpoint
export const GET = async () =>
  fetch("https://renderkit.keelhelm.com/v1/screenshot", {
    method: "POST",
    headers: { Authorization: `Bearer ${import.meta.env.RENDERKIT_KEY}`, "Content-Type": "application/json" },
    body: JSON.stringify({ url: "https://example.com" }),
  });

Authentication

Pass your secret key as a bearer token: Authorization: Bearer sk_…. Keys are created at signup and scoped to your account. For Open Graph images you embed in HTML, use your public key plus a signature (see below) so the secret never appears in a URL.

Screenshot

POST /v1/screenshot

Capture any URL or your own HTML as a PNG or JPEG. Viewport by default; full-page on request.

Field	Type	Notes
`url` / `html`	string	One is required (not both).
`full_page`	boolean	Capture the whole scroll height. Counts as 2 renders.
`format`	png · jpeg	Defaults to png.
`viewport_width` / `viewport_height`	number	Defaults 1280 × 800.
`response`	binary · url	Image bytes, or a JSON link to the cached result.

PDF

POST /v1/pdf

Turn a live page or your own markup into a paginated PDF. Counts as 2 renders.

Field	Type	Notes
`url` / `html`	string	One is required.
`format`	A4 · Letter	Defaults to A4.
`landscape`	boolean	Defaults to false.
`margin_mm`	number	Uniform page margin in millimetres.

curl -X POST https://renderkit.keelhelm.com/v1/pdf \
  -H "Authorization: Bearer sk_your_key" -H "Content-Type: application/json" \
  -d '{"url":"https://example.com","format":"A4"}' --output page.pdf

Open Graph image

GET /v1/og/:template.png

Generate the preview image that appears when a link is shared, from a reusable template. Because it's a plain GET, you embed it with a single tag — pass your public key and a signature so the URL is safe to ship in your HTML.

<!-- in your page <head> -->
<meta property="og:image"
  content="https://renderkit.keelhelm.com/v1/og/blog-header.png?title=Hello&pk=pk_you&sig=…">

Browse the template gallery for every template, its parameters, and a live example. Identical parameters return instantly from cache.

Limits & units

A screenshot or Open Graph image is one render; a full-page capture or a PDF is two; a cache hit is zero. Plans set a monthly render budget plus a per-minute rate — see pricing. Identical requests are served from cache and never counted.

Errors

Every error returns JSON: {"error":{"code","message","doc_url"}} with the right HTTP status.

Code	Status	Meaning
`unauthorized`	401	Missing or invalid key.
`bad_signature`	401	Open Graph signature didn't match the parameters.
`blocked_target`	400	The target URL isn't allowed (private/reserved address).
`rate_limited`	429	Too many requests this minute — slow down.
`quota_exceeded`	429	Monthly render budget reached.
`payload_too_large`	413	Inline HTML exceeds 2 MB.
`render_failed`	500	The page couldn't be rendered — retry.