CaptureKit Ruby SDK

The official Ruby SDK for the CaptureKit screenshot API.

Capture websites as PNG, JPEG, WebP or PDF, extract their content, or analyse them with AI.

The SDK exposes 7 methods, one per documented endpoint, plus a generic request. It only uses the Ruby standard library.

Requirements

• Ruby 3.1 or newer

Installation

gem install capturekitdev

Or in your Gemfile:

gem "capturekitdev"

Get your API key

Sign up for CaptureKit or sign in, then copy your API key from the dashboard. The client reads ENV["CAPTUREKIT_API_KEY"] when no key is passed.

Quick start

require "capturekit"

client = CaptureKit::Client.new(api_key: ENV.fetch("CAPTUREKIT_API_KEY"))
response = client.content(url: "https://example.com")
puts response.data

Keyword arguments use the parameter names of the API reference. Unknown names raise CaptureKit::SerializationError; use request for undocumented parameters.

Binary responses

Endpoints that can return a file (image, PDF…) return a JsonResponse or a BinaryResponse:

response = client.capture(url: "https://example.com", format: "png")
response.save("screenshot.png") if response.binary?

Async jobs

Any call accepts is_async: true (useful past the 60-second server limit): the response is then a job_id. wait_for_job polls GET /v1/jobs/{id} until a terminal status (CompletedJob, Error, NotFound, BadRequest):

submitted = client.content(url: "https://example.com", is_async: true)
job = client.wait_for_job(submitted.data["job_id"]) { |j| puts "#{j['status']} #{j['progress']}%" }
puts job.data

GET or POST

Methods use GET when the endpoint supports it (query string). POST sends the same parameters as JSON:

client.analyze(url: "test", request_options: { method: "POST" })

nil values are omitted, false and 0 are sent, and arrays repeat the parameter name.

Any endpoint

response = client.request("GET", "/v1/usage")

Errors

begin
  client.content(url: "https://example.com")
rescue CaptureKit::APIError => e
  warn "HTTP #{e.status}: #{e.message}"
end

Error	When
CaptureKit::ConfigurationError	Missing API key, invalid options or unsupported method.
CaptureKit::SerializationError	A required parameter is missing, unknown or can't be sent.
CaptureKit::TransportError	Network failure or timeout.
CaptureKit::APIError	Non-2xx status (status, error_message, response_body, raw_response).
CaptureKit::ResponseDecodingError	A success response could not be decoded.

All of them inherit from CaptureKit::Error.

Retries

Requests are retried up to 3 times after a network error, a 408, 500, 502, 503 or 504, or a rate limit — which the API returns as 401 (or 429) with a Rate limit exceeded message. Per-key quota errors (…: quota daily) are not retried, nor are 400, 402, 404 or client-side timeouts. The delay starts at 1 second and grows 1.5× per retry (capped at 30 seconds); a Retry-After header wins.

client = CaptureKit::Client.new(max_retries: 5, retry_delay: 0.5)
client.content(url: "https://example.com", request_options: { max_retries: 0 }) # one request without retries

Batch requests

batch runs the block for every item on 10 threads (concurrency:) and returns one BatchResult per item, in input order. A failing item never stops the others.

inputs = ["https://example.com", "https://www.capturekit.dev", "https://github.com"]
results = client.batch(inputs, concurrency: 5) { |value| client.content(url: value) }
results.each do |result|
  if result.ok?
    puts result.value.data
  else
    warn "#{inputs[result.index]}: #{result.error.message}"
  end
end

Constant	Default	Description
CaptureKit::Client::DEFAULT_CONCURRENCY	10	Tasks run at the same time by batch
CaptureKit::Client::DEFAULT_TIMEOUT	120	Request timeout (seconds)
CaptureKit::Client::MAX_RETRIES	3	Retry attempts after a network error, a 408/5xx or a rate limit
CaptureKit::Client::RETRY_BACKOFF_FACTOR	1.5	Exponential backoff multiplier
CaptureKit::Client::DEFAULT_RETRY_DELAY	1.0	Delay before the first retry (seconds)

Timeouts and custom transports

client = CaptureKit::Client.new(timeout: 60) # seconds, default 120
client.content(url: "https://example.com", request_options: { timeout: 30 })

A transport is any object with call(method:, url:, headers:, body:, timeout:) returning [status, headers, body]; the default is CaptureKit::NetHTTPTransport.

Endpoints

7 methods, generated from the OpenAPI document.

Method	HTTP	Description
analyze	GET / POST /v1/analyze	AI Content API analyzes any webpage and returns AI insights summary, value proposition, features, categories, use cases, and optional conta…
capture	GET / POST /v1/capture	Browser-like Screenshot API that captures webpages as PNG/JPEG/WebP or PDF for previews, QA, reporting, monitoring, and archiving no headle…
content	GET / POST /v1/content	CaptureKit Content API extracts structured webpage data, metadata, links, HTML/Markdown: in one request for SEO, monitoring, indexing and a…
jobs	GET /v1/jobs/{id}	Poll the status, progress (0–100) and result of a job started with is_async=true. Polling is free. Poll until status is terminal: Completed…
stats	GET /v1/stats	Infrastructure health for an engine or endpoint over the last hour. Not scoped to your account or tenant. Enabled per account: HTTP 403 mea…
usage	GET /v1/usage	Retrieve real-time usage statistics and credit balance for your CaptureKit account.
website_crawler	GET / POST /v1/website/crawler	Website Crawler API fetches raw HTML from any webpage in request mode (no rendering) for fast scraping, audits, monitoring, and link/metada…

All CaptureKit SDKs

SDK	Package	Install
Node.js	@capturekitdev/sdk	npm install @capturekitdev/sdk
Python	capturekitdev	pip install capturekitdev
Go	capturekit-go	go get github.com/capturekitdev/capturekit-go
.NET	CaptureKit	dotnet add package CaptureKit
Ruby	capturekitdev	gem install capturekitdev
PHP	capturekitdev/sdk	composer require capturekitdev/sdk
Java	capturekit-java	build from source, see its README
CLI	@capturekitdev/cli	npm install -g @capturekitdev/cli
MCP server	@capturekitdev/mcp	npx -y @capturekitdev/mcp

License

MIT — see LICENSE.