API reference

One base URL, JSON in, application/pdf out. Every endpoint below is live on https://renderpaper.com.

Authentication

Create a key under API keys in your account. Send it as either header — both work identically:

X-API-Key: rs_live_…
— or —
Authorization: Bearer rs_live_…

Your first render

The shortest path: post HTML and data together, get a PDF back in the response body. Nothing is stored.

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

# invoice.pdf — 1 page, A4

Template syntax

Templates are Go html/template. Every field of data is available by name, and values are HTML-escaped as they are injected, so customer-supplied text cannot break your layout or inject markup.

A template that fails to parse or execute returns 400 with the actual error message, so it is debuggable from the response rather than by guesswork.

Render inline HTML

Returns application/pdf. Use this when the template lives in your codebase.

Render a stored template

Returns application/pdf. Use this when someone other than a developer owns the design — you send only the data, and edits made in the editor apply to the next render with no code change.

{
  "data": { "Number": "2026-0142", "Customer": "Northwind Ltd" },
  "options": { "paper": "a4" }
}

Options

All optional, on every render endpoint.

Image output

Set format to png, jpeg or webp on any render endpoint and the response is that image instead of a PDF. Same template, same data, same metering — an image counts as one document, however tall it is.

$ curl -X POST https://renderpaper.com/v1/render \
    -H "X-API-Key: $RENDERPAPER_KEY" \
    -H "Content-Type: application/json" \
    -d '{"template":"<h1>{{.Title}}</h1>","data":{"Title":"Launch"},
         "options":{"format":"png","width":1200,"height":630}}' \
    -o card.png

# card.png — 1200x630 CSS pixels at 2x, ready for an og:image tag

Templates are self-contained

The renderer fetches nothing over the network — not images, not stylesheets, not fonts. That is a deliberate property: a render cannot leak data to a third host, cannot slow down on someone else's CDN, and cannot change because a remote file did.

For images, upload them in the editor — references to uploaded assets (/a/…) are inlined into the document automatically at render time — or embed a data: URI directly. For type, use the built-in font set (Liberation and Noto cover ordinary documents) or embed a font as @font-face with a data: source.

List templates

[
  {
    "id": "inv_8f2c1a",
    "name": "Invoice",
    "updated_at": "2026-08-04T09:12:44Z",
    "render_url": "https://renderpaper.com/v1/templates/inv_8f2c1a/render"
  }
]

Create a template

Returns 201 and the same object shape as the list endpoint. Templates created through the API are editable in the browser editor, and vice versa — there is one set of templates, not two.

Update a template

Same body as create. Renders that begin after the update use the new HTML; documents already accepted in a batch are unaffected, because a batch snapshots the template when it is accepted.

Delete a template

Returns 204. Deleting a template does not affect PDFs already rendered from it.

Submit a batch

For invoice and statement runs: one request instead of hundreds, with retries handled for you and no HTTP timeout hanging over the whole job. Returns 202 Accepted — the documents are queued, not finished.

{
  "batch_id": "bat_7d1e04",
  "count": 3,
  "status_url": "https://renderpaper.com/v1/batches/bat_7d1e04",
  "items": [
    { "id": "job_a1", "position": 0,
      "pdf_url": "https://renderpaper.com/v1/jobs/job_a1/pdf" }
  ]
}

Batch status

{
  "batch_id": "bat_7d1e04",
  "complete": false,
  "counts": { "total": 3, "queued": 1, "running": 1, "done": 1, "failed": 0 },
  "created_at": "2026-08-04T09:14:02Z",
  "items": [
    { "id": "job_a1", "position": 0, "status": "done",
      "pdf_bytes": 24518,
      "pdf_url": "https://renderpaper.com/v1/jobs/job_a1/pdf" }
  ]
}

Poll this until complete is true. An item that failed every attempt carries an error field explaining why.

Fetch a document

Returns application/pdf once the document is rendered.

Batch results are deleted automatically 24 hours after they are created, so fetch what you need within that window.

Completion webhooks

Add webhook_url to a batch and we POST the outcome to it once every document has settled — no polling. The URL must be https on a public host.

{
  "event": "batch.completed",
  "batch_id": "bat_7d1e04",
  "counts": { "total": 3, "done": 3, "failed": 0 },
  "items": [ { "id": "job_a1", "status": "done", "pdf_url": "…" } ],
  "timestamp": "2026-08-05T18:40:12Z"
}

Verifying the signature

Every delivery carries X-Renderpaper-Signature: hex(HMAC-SHA256(body, key)) where the key is hex(SHA256(your API key)) — derived from something you already hold, so there is no extra secret to store.

const key = crypto.createHash('sha256').update(process.env.RENDERPAPER_KEY).digest('hex');
const sig = crypto.createHmac('sha256', key).update(rawBody).digest('hex');
// compare sig with the X-Renderpaper-Signature header, constant-time

Zapier, Make and n8n

There is no marketplace app to install — the API is plain HTTP, which every automation tool already speaks. Three working recipes:

Zapier

Add a Webhooks by Zapier → Custom Request step: method POST, URL https://renderpaper.com/v1/render, headers X-API-Key and Content-Type: application/json, and the JSON body from your first render with fields mapped from earlier steps. The response is the PDF; feed it to any step that accepts a file.

Make

Use the HTTP → Make a request module with the same method, URL and headers. Body type Raw / JSON. Tick Parse response off — the response is binary — and map the output to Google Drive, email, or wherever the document goes.

n8n

An HTTP Request node, response format File. For batches, pair it with a Webhook node and pass that node's URL as webhook_url — n8n resumes when the batch completes, no polling loop.

These are recipes against the generic HTTP modules, not published marketplace apps; the field names above are exact.

Errors

Every error is JSON: {"error": "…"}.

Limits

Requests are also rate limited per account, and each plan includes a monthly document allowance — see pricing. On a paid plan, going over the allowance is billed rather than blocked, because a hard stop mid-run is the worse failure. On the free plan rendering stops at the allowance, since there is no card on file to bill the extra to. A failed render is never counted against the allowance.