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How to generate a PDF from HTML in Ruby on Rails

Call the Inkspan /v1/generate/html endpoint from Ruby on Rails to generate a PDF from HTML — no headless browser, font stack, or rendering infrastructure in your deploy. Keep your API key in the environment and POST.

send_data is the idiomatic way to return the PDF to a browser. Use Rails credentials or an environment variable for the key.

Ruby on Rails example

# app/controllers/pdf_controller.rb
require 'net/http'

def create
  uri = URI('https://api.inkspan.dev/v1/generate/html')
  res = Net::HTTP.post(uri, {"html": "<h1>Invoice</h1>"}.to_json, {
    'X-API-Key' => ENV.fetch('INKSPAN_KEY'),
    'Content-Type' => 'application/json',
  })

  raise res.body unless res.is_a?(Net::HTTPSuccess)
  send_data res.body, type: 'application/pdf', disposition: 'attachment'
end

Request parameters

Name	Type	Required	Description
`html`	string	yes	The HTML document or fragment to render.
`filename`	string	no	Filename in the response's Content-Disposition. Defaults to `document.pdf`.

Response

Returns a PDF as a binary stream with Content-Type: application/pdf and Content-Disposition: attachment; filename=document.pdf. Write the response body straight to disk — do not parse it as JSON.

Production notes

Wrap the call in a background job with Active Job if the document is large; a synchronous render blocks a Puma thread.

Relative URLs have no base to resolve against. Reference images and stylesheets with absolute https:// URLs, or inline them as data: URIs.
Page size and margins come from CSS, not from a parameter. Set @page { size: A4; margin: 18mm; } in your HTML to control them.
External resources are fetched server-side with SSRF protection, so private-network and file:// URLs are rejected. Host assets publicly or inline them.

Errors

Status	Meaning	Fix
`401`	Invalid or missing API key	Send your key in the `X-API-Key` header.
`402`	Monthly quota exceeded	The response reports used/quota. Upgrade at inkspan.dev/#pricing.
`422`	Missing or invalid parameter	Check required fields in the table above — the body names the offending field.

Failed requests do not count against your quota; only successful ones are metered.

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Same operation in cURL · Python · Node.js · Other frameworks: Next.js · Django · Laravel · PHP · All guides