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Convert a URL to PDF in Ruby with Net::HTTP

The baseline job: give the API a URL, get PDF bytes back. One POST, binary response, no callback dance — the body of the response is the file. Everything else on this page is about doing that reliably: auth, error handling, and not treating a JSON error as a PDF.

Below is a complete, runnable Ruby program using Net::HTTP, no third-party dependency needed. It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

require "json"
require "net/http"
require "uri"

uri = URI("https://snapdok.io/v1/render")

res = Net::HTTP.start(uri.host, uri.port, use_ssl: true, read_timeout: 90) do |http|
  req = Net::HTTP::Post.new(uri)
  req["Authorization"] = "Bearer #{ENV.fetch("SNAPDOK_KEY")}"
  req["Content-Type"] = "application/json"
  req.body = JSON.generate({
    url: "https://your-app.com/report/42",
    format: "pdf",
})
  http.request(req)
end

raise "snapdok error #{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)

File.binwrite("page.pdf", res.body)

The response is the document itself with Content-Type: application/pdf. Errors come back as JSON with an error code — which is why every sample here checks the status before writing bytes to disk: the classic integration bug in every language is saving {"error":"UNAUTHORIZED"...} as report.pdf and discovering it a week later.

PDF rendering uses the page's print stylesheet and reflows to paper width, so the width parameter does not apply to PDFs (it is a screenshot concept). If a page looks wrong as PDF, its @media print CSS is usually the culprit. Repeated identical requests inside 24 hours are served from cache — X-Cache: HIT — and not charged.

Same endpoint, one more trick: if the page you are rendering has a form on it, adding "pdf_forms": true to a PDF render brings it back with real, fillable AcroForm fields — a PDF people can type into, not a picture of one. How that works.

Notes for Net::HTTP

Stdlib only — no gems. The traps Net::HTTP is famous for, all handled in the sample: TLS is not automatic (set use_ssl: true or you will POST in the clear to port 80 and get a redirect); the default read_timeout of 60 s is close enough to real render times that raising it is wise; and the response body is a binary-ready String, but write it with File.binwrite — plain File.write on Windows would mangle line-ending bytes in the PDF. Check is_a?(Net::HTTPSuccess): Net::HTTP never raises on HTTP error statuses.

Response headers worth reading

HeaderMeaning
X-CacheHIT = served from the 24h cache, free.
X-RateLimit-RemainingRequests left in the current second.

Full parameter reference: the docs. Hard numbers on caps and timeouts: limits.

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