Error map
ERR_QUIC_PROTOCOL_ERROR Chrome: This site can’t be reached — ERR_QUIC_PROTOCOL_ERROR (HTTP/3 over UDP blocked)
Browser · layer 1, On your device
Centre: this error. First ring: errors it is linked with (10). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (10)
HTTP 100 Continue
An interim response telling the client to go ahead and send the request body — normal when the client sent Expect: 100-continue.
Cloudflare Error 1200: Cache connection limit
Too many requests are queued at Cloudflare for the origin — the origin is slow and connections pile up.
HTTP 505 HTTP Version Not Supported
The server doesn’t support the HTTP protocol version used in the request.
HTTP 103 Early Hints
An interim response that sends Link headers early so the browser can preload CSS, fonts or scripts while the server is still buil…
Chrome: This site can’t be reached — The webpage at https://… might be temporarily down. ERR_ADDRESS_UNREACHABLE
The computer has no route to the server’s IP address — often an IPv6 problem, a wrong local-network address, or a VPN routing iss…
Chrome: This site can’t be reached — example.com unexpectedly closed the connection. ERR_CONNECTION_CLOSED
The server closed the connection before finishing the TLS handshake or sending a response — typical for HTTP/HTTPS port mix-ups,…
Chrome: This page isn’t working — example.com is unable to handle this request. ERR_HTTP2_PROTOCOL_ERROR
The HTTP/2 connection broke a protocol rule — a server, proxy or CDN sent an invalid or oversized frame/header, or closed the str…
Chrome: This site can’t be reached — server IP address could not be found. DNS_PROBE_FINISHED_NXDOMAIN
The DNS server answered that the domain name does not exist (NXDOMAIN) — a typo, an expired or unregistered domain, a missing DNS…
Chrome: No internet — DNS_PROBE_FINISHED_NO_INTERNET (DNS probe finished, no internet)
Chrome’s built-in DNS probe could not reach any DNS server, so the device effectively has no working internet or DNS.
Browser: This network requires you to sign in — captive portal (hotel, airport, café Wi-Fi) blocking HTTPS sites
The Wi-Fi needs a login or acceptance page first; until you complete it, secure sites fail with certificate or connection errors.
Two steps away (29)
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
Warning: Cannot modify header information - headers already sent
You called `header()`, `setcookie()` or `session_start()` after output had already been sent to the browser.
CORS Error: No 'Access-Control-Allow-Origin' header is present
The browser blocked a cross-origin request because the server’s response didn’t include the CORS headers allowing your site’s ori…
HTTP 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, in maintenance, or has no healthy backends.
HTTP 504 Gateway Timeout
A proxy or gateway waited too long for the upstream server to respond and gave up.
Cloudflare Error 524: A Timeout Occurred
Cloudflare connected to the origin, but the origin didn’t send an HTTP response within 100 seconds.
HTTP 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
HTTP 501 Not Implemented
The server doesn’t support the functionality (usually the HTTP method) needed to fulfil the request.
HTTP 304 Not Modified
The cached copy is still valid, so the server sends no body and the client reuses its cache.
HTTP 411 Length Required
The server refuses a request with a body but no Content-Length header.
HTTP 200 OK (but something is still wrong)
The request succeeded at the HTTP level — yet the page is blank, the data is wrong, or an error is hidden inside the response bod…
net::ERR_NAME_NOT_RESOLVED (This site can't be reached — server IP address could not be found)
DNS couldn’t resolve the hostname in the browser.
ERR_CONNECTION_TIMED_OUT: This site can’t be reached — example.com took too long to respond
The browser waited for the server but got no response — the server is down/unreachable, a firewall drops traffic, or DNS points t…
Chrome: No internet — ERR_INTERNET_DISCONNECTED (You are not connected to the internet)
Chrome sees no working network connection on the device, so it cannot load any page.
Cloudflare Error 525: SSL Handshake Failed
Cloudflare couldn’t complete a TLS handshake with your origin (SSL mode Full / Full strict).
Cloudflare Error 526: Invalid SSL Certificate
With SSL mode Full (strict), the origin’s certificate is expired, self-signed, or doesn’t match the hostname.
ERR_CONNECTION_RESET: This site can’t be reached — The connection was reset
The connection to the website was cut off mid-way — by the server, a firewall/antivirus, a VPN/proxy, or network equipment.
HTTP 431 Request Header Fields Too Large
The request headers — almost always cookies — exceed the server’s size limit.
Chrome: This page isn’t working — example.com didn’t send any data. ERR_EMPTY_RESPONSE
The server accepted the connection but closed it without sending any HTTP response — a crash, timeout or misconfigured proxy on t…
Chrome: This page isn’t working — example.com redirected you too many times. ERR_TOO_MANY_REDIRECTS
The page keeps redirecting to itself or in a loop, so the browser gives up after about 20 redirects.
HTTP 408 Request Timeout
The server closed the connection because the client took too long to send the complete request.
TypeError: Failed to fetch / NetworkError when attempting to fetch resource
The browser couldn’t complete the request at the network level — CORS, DNS, offline, blocked mixed content, or the server refused…
API Request Timed Out (ETIMEDOUT / ReadTimeout / timeout of 30000ms exceeded)
The client gave up waiting — either for the connection to open or for the response to arrive.
Error: socket hang up / read ECONNRESET
The other side closed the TCP connection abruptly while your client was still using it.
Error: getaddrinfo ENOTFOUND host / Name or service not known
DNS lookup for the hostname failed — the name is wrong, doesn’t exist, or this machine can’t resolve it.
net::ERR_BLOCKED_BY_CLIENT
A browser extension (ad blocker, privacy tool) blocked the request.
HTTP 407 Proxy Authentication Required
A proxy between you and the server requires credentials before it will forward your request.
net::ERR_CONNECTION_REFUSED (This site can't be reached — refused to connect)
The browser reached the host but nothing was listening on that port.
NET::ERR_CERT_AUTHORITY_INVALID (Your connection is not private)
The site’s certificate isn’t signed by a CA the browser trusts — self-signed, missing intermediates, or intercepted by a proxy.
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