CaptureKit .NET SDK

The official .NET 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 typed async methods, one per documented endpoint (with required properties checked at compile time), plus a generic RequestAsync.

Requirements

• .NET 8 or newer

Installation

dotnet add package CaptureKit

Get your API key

Sign up for CaptureKit or sign in, then copy your API key from the dashboard. new CaptureKitClient() reads the CAPTUREKIT_API_KEY environment variable.

Quick start

using CaptureKit;

using var client = new CaptureKitClient();
var response = await client.ContentAsync(new ContentParams { Url = "https://example.com" });
Console.WriteLine(response.Json);

Parameter classes mirror the API reference. Use response.Deserialize<MyType>() to map the JSON onto your own types.

Binary responses

Endpoints that return a file (image, PDF…) give you the bytes; IsJson tells both cases apart:

var response = await client.CaptureAsync(new CaptureParams { Url = "https://example.com", Format = "png" });
if (!response.IsJson)
{
    await File.WriteAllBytesAsync("screenshot.png", response.Bytes);
}

Async jobs

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

var submitted = await client.ContentAsync(new ContentParams { Url = "https://example.com", IsAsync = true });
var job = await client.WaitForJobAsync(
    submitted.Json.GetProperty("job_id").GetString()!,
    onProgress: j => Console.WriteLine($"{j.GetProperty("status")} {j.GetProperty("progress")}%"));

GET or POST

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

await client.AnalyzeAsync(new AnalyzeParams { Url = "test" }, new RequestOptions { Method = "POST" });

Any endpoint

var response = await client.RequestAsync("GET", "/v1/usage");

Errors

try
{
    await client.ContentAsync(new ContentParams { Url = "https://example.com" });
}
catch (CaptureKitApiException exception)
{
    Console.Error.WriteLine($"{exception.StatusCode}: {exception.Message}");
}

Exception	When
CaptureKitConfigurationException	Missing API key, invalid options or unsupported method.
CaptureKitSerializationException	A required parameter is missing or a value can't be sent.
CaptureKitTransportException	Network failure or timeout.
CaptureKitApiException	Non-2xx status (StatusCode, ErrorMessage, ResponseBody, RawResponse).
CaptureKitResponseDecodingException	A success response could not be decoded.

All of them derive from CaptureKitException. Caller cancellation surfaces as OperationCanceledException.

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.

using var client = new CaptureKitClient(new CaptureKitClientOptions { MaxRetries = 5, RetryDelay = TimeSpan.FromMilliseconds(500) });
await client.ContentAsync(new ContentParams { Url = "https://example.com" }, new RequestOptions { MaxRetries = 0 }); // one request without retries

Batch requests

BatchAsync runs a function per item with at most 10 in flight (concurrency) and returns one BatchResult per item, in input order. A failing item never stops the others.

string[] inputs = { "https://example.com", "https://www.capturekit.dev", "https://github.com" };
var results = await client.BatchAsync(inputs, (value, ct) =>
    client.ContentAsync(new ContentParams { Url = value }, cancellationToken: ct), concurrency: 5);
foreach (var result in results)
{
    if (result.Ok)
    {
        Console.WriteLine(result.Value!.Json);
    }
    else
    {
        Console.Error.WriteLine($"{inputs[result.Index]}: {result.Error!.Message}");
    }
}

Constant	Default	Description
CaptureKitClient.DefaultConcurrency	10	Tasks run at the same time by batch
CaptureKitClient.DefaultTimeout	TimeSpan.FromSeconds(120)	Request timeout
CaptureKitClient.MaxRetries	3	Retry attempts after a network error, a 408/5xx or a rate limit
CaptureKitClient.RetryBackoffFactor	1.5	Exponential backoff multiplier
CaptureKitClient.DefaultRetryDelay	TimeSpan.FromSeconds(1)	Delay before the first retry

Configuration

using var client = new CaptureKitClient(new CaptureKitClientOptions
{
    ApiKey = Environment.GetEnvironmentVariable("CAPTUREKIT_API_KEY"),
    Timeout = TimeSpan.FromSeconds(60), // default 120 s
    HttpClient = myHttpClient,           // optional, you keep ownership
});

Endpoints

7 methods, generated from the OpenAPI document.

Method	HTTP	Description
AnalyzeAsync	GET / POST /v1/analyze	AI Content API analyzes any webpage and returns AI insights summary, value proposition, features, categories, use cases, and optional conta…
CaptureAsync	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…
ContentAsync	GET / POST /v1/content	CaptureKit Content API extracts structured webpage data, metadata, links, HTML/Markdown: in one request for SEO, monitoring, indexing and a…
JobsAsync	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…
StatsAsync	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…
UsageAsync	GET /v1/usage	Retrieve real-time usage statistics and credit balance for your CaptureKit account.
WebsiteCrawlerAsync	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.