URL Reachability¶

URL reachability checks answer a simple question: does this URL load? Two implementations exist, with different tradeoffs.

Choosing a Checker¶

Checker	Transport	Detects	Cost
`WebAccessService` (`IWebAccessService`)	Plain HTTP	HTTP status, redirects	Low
Content fetchers (`IWebContentFetcher`)	Rendered browser	HTTP status, browser error pages	High

WebAccessService — Plain HTTP¶

Registered by AddWebToolsCore(). Sends real browser-like headers, keeps a cookie container, decompresses responses, and tracks redirects manually.

var webAccess = provider.GetRequiredService<IWebAccessService>();

var check = await webAccess.CheckReachabilityAsync("https://test.example.com");
Console.WriteLine($"{check.Reachable} (HTTP {check.HttpStatus}, " +
                  $"{check.RedirectCount} redirects, final: {check.FinalUrl})");

Behavior details:

Follows up to 10 redirects; more yields Reachable = false with a "too many redirects" error
A URL is reachable when the final status is 2xx or 3xx (excluding 304)
15 second overall request timeout; timeouts yield ErrorMessage = "Timed out"
Handles both absolute and relative Location headers

Warning

Plain HTTP cannot execute JavaScript. Pages that only fail inside a browser (bot walls, client-side errors) still report reachable here. Use a browser-based check when that matters.

Browser-Based Checks¶

IWebContentFetcher.CheckReachabilityAsync loads the page in the configured browser engine and reports Reachable only when the response status is 2xx and the final URL is not a browser error page.

var check = await fetcher.CheckReachabilityAsync("https://test.example.com");

Useful for validating links discovered by the WebNavigationAgent, which performs exactly this kind of check internally.

The UrlCheckResult Model¶

Property	Description
`Reachable`	Whether the URL loaded successfully
`HttpStatus`	Final HTTP status code, when available
`ErrorMessage`	Failure reason, when not reachable
`RedirectCount`	Number of redirects followed
`FinalUrl`	URL after redirects
`ProtectionType`	Detected protection type, when reported by the engine