HttpClientHandler

HttpClientHandler is a concrete implementation of HttpMessageHandler in the System.Net.Http namespace and is used by HttpClient to send requests and receive responses. It exposes transport-level configuration that affects cookies, redirects, decompression, proxy usage, and client authentication. By adjusting its properties, applications can tailor how HTTP traffic is processed without changing the higher-level HttpClient code.

Key capabilities include controlling redirection with AllowAutoRedirect, enabling automatic decompression for responses through AutomaticDecompression (for methods such as gzip and deflate), and managing cookies via UseCookies and a CookieContainer. Proxy settings are exposed through UseProxy and Proxy, while authentication can be supplied with UseDefaultCredentials or explicit Credentials. Client TLS certificates can be configured with ClientCertificates and ClientCertificateOptions, and TLS validation can be customized with ServerCertificateCustomValidationCallback. For performance and resource management, properties such as PooledConnectionIdleTimeout, PooledConnectionLifetime, and MaxConnectionsPerServer are available to tune connection pooling and lifetimes across requests.

Typical usage involves creating an HttpClientHandler, configuring the desired properties, and passing the handler to the HttpClient constructor. This enables a single handler to govern multiple requests, promoting reuse and more predictable behavior than creating a new handler per request.

Platform considerations may affect the available features or defaults across different runtimes. While HttpClientFactory can simplify handler reuse and lifetime management in applications, HttpClientHandler remains the foundational transport configuration mechanism for HttpClient in many .NET environments.