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Take a screenshot of a URL in Ruby with Net::HTTP

The simplest request the API takes: a URL in, PNG bytes out. No full_page, no extra options — you get exactly what a visitor with a 1280×800 browser window would see above the fold. That is the right default more often than people expect: link previews, monitoring thumbnails and visual smoke tests all want the fold, not a 40,000-pixel scroll of the footer.

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: "png",
    width: 1280,
    height: 800,
})
  http.request(req)
end

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

File.binwrite("screenshot.png", res.body)

The two dimensions are the viewport, not the output size: the page lays itself out as if the browser window were 1280×800, and the image comes back at exactly those pixels (multiply by device_scale if you set it). Responsive sites react to the width — ask for 390 and you get the mobile layout, no user-agent spoofing involved.

Two habits worth starting on day one. Check the HTTP status before writing bytes to disk — errors arrive as JSON, and saving {"error":"UNAUTHORIZED"} as screenshot.png is the classic first-week bug. And log the X-Cache header: identical requests within 24 hours return HIT, cost nothing, and come back in milliseconds — failed renders are never metered either way.

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

Header	Meaning
`X-Cache`	HIT = served from the 24h cache, free.
`X-Quota-Remaining`	Metered renders left this month.
`X-RateLimit-Remaining`	Requests left in the current second.

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

Take a screenshot of a URL in Ruby with Net::HTTP

Notes for Net::HTTP

Response headers worth reading

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