How to use the Open Library API in C#

Books, book covers and related data. This guide calls it from C# with code we've run against the live endpoint.

Online · 1547 msEndpoint tested Oct 24, 2026

1. What you need

.NET 6 or newer. Paste into a top-level `Program.cs` and run `dotnet run`.

No API key or sign-up. Endpoint: https://openlibrary.org/developers/api

2. Make the request

using System.Net.Http;

using var http = new HttpClient { Timeout = TimeSpan.FromSeconds(10) };
var json = await http.GetStringAsync("https://openlibrary.org/developers/api");
Console.WriteLine(json);

3. The response

Trimmed from the live response on Oct 24, 2026.

JSON

{
  "body": {
    "type": "/type/text",
    "value": "## Getting Started\r\n\r\nOpen Library provides APIs in JSON, YAML and RDF/XML fo..."
  },
  "title": "APIs",
  "m": "edit",
  "key": "/developers/api",
  "type": {
    "key": "/type/page"
  },
  "latest_revision": 108,
  "revision": 108,
  "created": {
    "type": "/type/datetime",
    "value": "2009-11-12T21:02:23.663490"
  },
  "last_modified": {
    "type": "/type/datetime",
    "value": "2026-10-09T10:08:45.093766"
  }
}

4. Before you ship

Set a timeout and handle non-200 responses: free APIs can rate-limit or go down.
Cache responses where you can, instead of calling the API on every page view.
Read the official documentation ↗ for rate limits and terms of use.

FAQ

Does the Open Library API need an API key in C#?

No. The Open Library API works without an API key, so the C# example runs as-is.

Can I call the Open Library API from the browser?

Not reliably: it doesn't send CORS headers. Call it from a server, serverless function or script.

What does the Open Library API return?

JSON. The example response on this page is trimmed from a real response our health check received on Oct 24, 2026.

Same API in: Python · Node.js · PHP · Java · Go · Ruby
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