Prerequisites
- .NET 6.0+
- A Firecrawl API key — get one free
Configuration
Add your API key toappsettings.json:
{
"Firecrawl": {
"ApiKey": "fc-YOUR-API-KEY",
"BaseUrl": "https://api.firecrawl.dev/v2"
}
}
export Firecrawl__ApiKey=fc-YOUR-API-KEY
Create a service
CreateServices/FirecrawlService.cs:
using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;
public class FirecrawlService
{
private readonly HttpClient _http;
private readonly string _baseUrl;
public FirecrawlService(IConfiguration config)
{
_baseUrl = config["Firecrawl:BaseUrl"] ?? "https://api.firecrawl.dev/v2";
_http = new HttpClient();
_http.DefaultRequestHeaders.Authorization =
new AuthenticationHeaderValue("Bearer", config["Firecrawl:ApiKey"]);
}
public async Task<JsonDocument> SearchAsync(string query, int limit = 5)
{
var content = new StringContent(
JsonSerializer.Serialize(new { query, limit }),
Encoding.UTF8, "application/json");
var response = await _http.PostAsync($"{_baseUrl}/search", content);
response.EnsureSuccessStatusCode();
return JsonDocument.Parse(await response.Content.ReadAsStringAsync());
}
public async Task<JsonDocument> ScrapeAsync(string url)
{
var content = new StringContent(
JsonSerializer.Serialize(new { url }),
Encoding.UTF8, "application/json");
var response = await _http.PostAsync($"{_baseUrl}/scrape", content);
response.EnsureSuccessStatusCode();
return JsonDocument.Parse(await response.Content.ReadAsStringAsync());
}
public async Task<JsonDocument> InteractAsync(string url, string prompt, string? followUp = null)
{
// 1. Scrape to open a browser session
var scrapeContent = new StringContent(
JsonSerializer.Serialize(new { url, formats = new[] { "markdown" } }),
Encoding.UTF8, "application/json");
var scrapeRes = await _http.PostAsync($"{_baseUrl}/scrape", scrapeContent);
scrapeRes.EnsureSuccessStatusCode();
var scrapeDoc = JsonDocument.Parse(await scrapeRes.Content.ReadAsStringAsync());
var scrapeId = scrapeDoc.RootElement
.GetProperty("data").GetProperty("metadata").GetProperty("scrapeId").GetString();
// 2. Send first prompt
var firstPrompt = new StringContent(
JsonSerializer.Serialize(new { prompt }),
Encoding.UTF8, "application/json");
await _http.PostAsync($"{_baseUrl}/scrape/{scrapeId}/interact", firstPrompt);
// 3. Send follow-up prompt
JsonDocument? result = null;
if (followUp != null)
{
var followUpContent = new StringContent(
JsonSerializer.Serialize(new { prompt = followUp }),
Encoding.UTF8, "application/json");
var followUpRes = await _http.PostAsync(
$"{_baseUrl}/scrape/{scrapeId}/interact", followUpContent);
followUpRes.EnsureSuccessStatusCode();
result = JsonDocument.Parse(await followUpRes.Content.ReadAsStringAsync());
}
// 4. Close the session
await _http.DeleteAsync($"{_baseUrl}/scrape/{scrapeId}/interact");
return result ?? scrapeDoc;
}
}
Register and use
InProgram.cs:
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddSingleton<FirecrawlService>();
var app = builder.Build();
app.MapPost("/api/search", async (FirecrawlService firecrawl, SearchRequest req) =>
{
var result = await firecrawl.SearchAsync(req.Query, req.Limit);
return Results.Ok(result.RootElement);
});
app.MapPost("/api/scrape", async (FirecrawlService firecrawl, ScrapeRequest req) =>
{
var result = await firecrawl.ScrapeAsync(req.Url);
return Results.Ok(result.RootElement);
});
app.MapPost("/api/interact", async (FirecrawlService firecrawl, InteractRequest req) =>
{
var result = await firecrawl.InteractAsync(req.Url, req.Prompt, req.FollowUp);
return Results.Ok(result.RootElement);
});
app.Run();
record SearchRequest(string Query, int Limit = 5);
record ScrapeRequest(string Url);
record InteractRequest(string Url, string Prompt, string? FollowUp = null);
Run it
dotnet run
Test it
# Search the web
curl -X POST http://localhost:5000/api/search \
-H "Content-Type: application/json" \
-d '{"query": "firecrawl web scraping"}'
# Scrape a page
curl -X POST http://localhost:5000/api/scrape \
-H "Content-Type: application/json" \
-d '{"url": "https://example.com"}'
# Interact with a page
curl -X POST http://localhost:5000/api/interact \
-H "Content-Type: application/json" \
-d '{"url": "https://www.amazon.com", "prompt": "Search for iPhone 16 Pro Max", "followUp": "Click on the first result and tell me the price"}'
Next steps
Search docs
Search the web and get full page content
Scrape docs
All scrape options including formats, actions, and proxies
Interact docs
Click, fill forms, and extract dynamic content
API Reference
Complete REST API documentation

