HTML in, PDF out — one HTTP request.

Send a template and your data. Get back a PDF you can put in front of a customer.

$ curl -X POST https://renderpaper.com/v1/render \
    -H "X-API-Key: $RENDER_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{"template":"<h1>Invoice {{.Nr}}</h1>","data":{"Nr":"2026-0142"}}' \
    -o invoice.pdf

# invoice.pdf — 1 page, A4

The {{.Nr}} placeholder is Go html/template syntax: every field in data is available by name, and values are escaped as they are injected.

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How it works

You POST an HTML template plus JSON data, headless Chromium renders it, and the PDF comes back in the response body — no polling, no callback URL, no file storage to clean up afterwards.

Because the renderer is a current Chromium, modern CSS just works: flexbox and grid for layout, web fonts, @page rules for paper size and margins, background colours and gradients. Templates that older PDF libraries quietly mangle come out looking like the page you designed.

Pricing

$29 / month

Flat rate

No per-render charges, no metered billing
Every rendering option included — paper size, orientation, margins, backgrounds
Full Chromium CSS support, not a subset
Cancel any time

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API reference

POST /v1/render

Returns application/pdf on success. Request bodies are capped at 1 MiB.

Authentication

Send your key as X-API-Key: <key> or Authorization: Bearer <key>. Either header works.

Body

Field	Type	Notes
template	string	Required. HTML, with optional template placeholders.
data	any JSON	Values injected into the template — objects, arrays, scalars.
options	object	Optional. See below.

Options

Field	Type	Default
paper	"a4" \| "letter"	"a4"
landscape	boolean	false
print_background	boolean	true
margin_in	number (inches)	0.4

A @page rule in your own CSS takes precedence over paper, so templates stay portable.

Errors

Status	Meaning
400	Invalid template or data — the parse or execution error is returned so you can fix it.
401	Missing or invalid API key.
503	At capacity. Retry shortly; a `Retry-After` header is set.
500	Render failure on our side.

Errors come back as JSON: {"error": "…"}.