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Website Down Detector

Check if a website is down for everyone or just you. Diagnostic tool for DNS, HTTP status codes, and server latency.

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Category Network Utilities

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Real-time availability diagnostic

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    About

    This tool performs a real-time diagnostic analysis of a target website's availability using a hybrid checking mechanism. It distinguishes between a Local Outage (specific to your network/ISP) and a Global Outage (server-side failure).

    The reachability algorithm measures the Round Trip Time (RTT) and interprets the HTTP Response Code (e.g., 200 vs 503). By attempting connections from both your browser and an external relay, we calculate the Probability of downtime with high accuracy.

    uptime server status ping website check is it down

    Formulas

    The availability status S is determined by the boolean conjunction of Local Reachability (L) and Global Reachability (G).

    S =
    {
    UP if L &lor; GDOWN if ¬L ∧ ¬G

    Latency (RTT) is calculated as the differential between the request timestamp (tstart) and response timestamp (tend).

    RTT = tend − tstart

    Reference Data

    CodeStatusMeaning
    200OKThe server is up and returned content successfully.
    301MovedPermanent redirect. Usually considers the site "UP".
    403ForbiddenServer is up but refusing access (firewall/permission).
    404Not FoundServer is up, but the specific page is missing.
    408TimeoutServer took too long to process the request.
    500Server ErrorInternal error. The server is technically "UP" but broken.
    502Bad GatewayUpstream server sent an invalid response.
    503UnavailableServer is overloaded or down for maintenance.
    504Gateway TimeoutUpstream server failed to respond in time.
    ERRConnection RefusedDNS failure or total network unreachable.

    Frequently Asked Questions

    The tool checks connectivity. If the server returns a status code like 200 OK or even 500 Error, the server is technically reachable (UP), even if it serves broken content. We detect if the machine is on, not if the design is broken.
    A Local Check attempts to connect from your specific device and IP. A Global Check uses an external proxy server. If Local fails but Global works, the issue is likely your ISP, DNS, or Firewall.
    Yes, the Local Check runs inside your browser, so it can detect localhost (e.g., 127.0.0.1) or internal IP addresses that external tools cannot see.
    Some websites have strict CORS (Cross-Origin Resource Sharing) policies or firewalls that block automated checks. We use a "no-cors" mode to bypass this where possible, but strict blocks may generate false negatives.
    Yes, extremely minimal bandwidth. It sends a single HEAD or GET request to the target URL to verify the handshake.