Async & webhooks

For big PDFs, full-page screenshots, or high volume, render asynchronously: enqueue the job, get an id back immediately, then either poll or receive a signed webhook.

# Enqueue

Add async: true (or a webhookUrl) to any render or screenshot request:

bash

curl https://api.mostlyrender.com/v1/renders \
  -H "Authorization: Bearer mr_live_…" \
  -H "Content-Type: application/json" \
  -d '{
    "template": "tpl_abc",
    "output": "pdf",
    "async": true,
    "webhookUrl": "https://your.app/hooks/mostlyrender"
  }'

json

{ "id": "job_xyz789", "status": "queued" }

The response is 202 Accepted with a job id.

# Poll

bash

curl https://api.mostlyrender.com/v1/renders/job_xyz789 \
  -H "Authorization: Bearer mr_live_…"

json

{
  "id": "job_xyz789",
  "status": "done",
  "kind": "render",
  "result": { "id": "rnd_abc", "url": "https://img.mostlyrender.com/…/rnd_abc.pdf", "output": "pdf" },
  "error": null
}

status moves queued → processing → done (or error). When done, result holds the render { id, url, output }.

python

job = mr.render_async("tpl_abc", output="pdf", webhook_url="https://your.app/hooks/mostlyrender")
final = mr.wait_for_render(job["id"])
print(final["result"]["url"])

# Webhooks

If you pass a webhookUrl, MostlyRender POSTs the job result there when it finishes:

json

{
  "id": "job_xyz789",
  "status": "done",
  "result": { "id": "rnd_abc", "url": "https://img.mostlyrender.com/…/rnd_abc.pdf", "output": "pdf" }
}

# Verify the signature

Each webhook carries an HMAC-SHA256 signature of the raw body in the x-mostlyrender-signature header, prefixed sha256=. Recompute it with your signing secret and compare in constant time:

import crypto from 'node:crypto';

function verify(rawBody, header, secret) {
  const expected = 'sha256=' + crypto.createHmac('sha256', secret).update(rawBody).digest('hex');
  return crypto.timingSafeEqual(Buffer.from(header), Buffer.from(expected));
}

Respond with any 2xx to acknowledge. Delivery is retried a few times on failure; webhook targets are SSRF-guarded just like screenshot URLs.