Making HEAD Requests with HttpClient in C

A HEAD request retrieves metadata about a resource without downloading its content body. This makes it ideal for checking resource availability, content type, or file size without the overhead of a full GET request.

Basic HEAD Request

Use HttpClient.SendAsync() with an HttpRequestMessage configured for HEAD requests:

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using var client = new HttpClient();
        using var request = new HttpRequestMessage(HttpMethod.Head, "https://example.com");

        try
        {
            using var response = await client.SendAsync(request);

            Console.WriteLine($"Status: {response.StatusCode}");
            Console.WriteLine($"Content-Type: {response.Content.Headers.ContentType}");
            Console.WriteLine($"Content-Length: {response.Content.Headers.ContentLength}");
            Console.WriteLine($"Last-Modified: {response.Content.Headers.LastModified}");
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine($"Request failed: {ex.Message}");
        }
    }
}

Extracting Useful Information

HEAD requests are commonly used to check specific resource properties:

public static async Task<bool> CheckResourceExists(string url)
{
    using var client = new HttpClient();
    using var request = new HttpRequestMessage(HttpMethod.Head, url);

    try
    {
        using var response = await client.SendAsync(request);
        return response.IsSuccessStatusCode;
    }
    catch
    {
        return false;
    }
}

public static async Task<long?> GetContentLength(string url)
{
    using var client = new HttpClient();
    using var request = new HttpRequestMessage(HttpMethod.Head, url);

    try
    {
        using var response = await client.SendAsync(request);
        return response.Content.Headers.ContentLength;
    }
    catch
    {
        return null;
    }
}

Advanced Example with Headers

For production code, include custom headers and proper error handling:

public class HttpHeadService
{
    private readonly HttpClient _httpClient;

    public HttpHeadService()
    {
        _httpClient = new HttpClient();
        _httpClient.DefaultRequestHeaders.Add("User-Agent", "MyApp/1.0");
    }

    public async Task<HeadRequestResult> GetResourceInfo(string url)
    {
        using var request = new HttpRequestMessage(HttpMethod.Head, url);

        try
        {
            using var response = await _httpClient.SendAsync(request);

            return new HeadRequestResult
            {
                IsSuccess = response.IsSuccessStatusCode,
                StatusCode = response.StatusCode,
                ContentType = response.Content.Headers.ContentType?.MediaType,
                ContentLength = response.Content.Headers.ContentLength,
                LastModified = response.Content.Headers.LastModified?.DateTime,
                Server = response.Headers.Server?.ToString()
            };
        }
        catch (HttpRequestException ex)
        {
            return new HeadRequestResult
            {
                IsSuccess = false,
                ErrorMessage = ex.Message
            };
        }
    }

    public void Dispose() => _httpClient?.Dispose();
}

public class HeadRequestResult
{
    public bool IsSuccess { get; set; }
    public HttpStatusCode StatusCode { get; set; }
    public string ContentType { get; set; }
    public long? ContentLength { get; set; }
    public DateTime? LastModified { get; set; }
    public string Server { get; set; }
    public string ErrorMessage { get; set; }
}

Best Practices

• Reuse HttpClient: Create one instance per application lifetime to avoid socket exhaustion
• Use HTTPS: Always use secure URLs when possible
• Handle exceptions: Wrap requests in try-catch blocks for network failures
• Set timeouts: Configure appropriate timeout values for your use case
• Check status codes: Always verify IsSuccessStatusCode before processing headers

Common Use Cases

• File size checking: Get content length before downloading large files
• Cache validation: Check Last-Modified headers for conditional requests
• Link verification: Validate URLs without downloading content
• API health checks: Test endpoint availability efficiently