Error map
307 HTTP 307 Temporary Redirect
HTTP · layer 2, Network
Centre: this error. First ring: errors it is linked with (12). 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 (12)
HTTP 302 Found (Temporary Redirect)
The resource is temporarily at another URL; clients should keep using the original URL for future requests.
HTTP 421 Misdirected Request
The request reached a server that isn’t configured for that host name — usually HTTP/2 connection reuse across domains sharing a…
ERR_TOO_MANY_REDIRECTS with Cloudflare (Flexible SSL redirect loop)
The page redirects to itself forever — classic cause: Cloudflare SSL mode “Flexible” while the origin redirects HTTP to HTTPS.
Mixed Content: The page was loaded over HTTPS, but requested an insecure resource
An HTTPS page tried to load a script, API or image over plain HTTP, and the browser blocked (or warned about) it.
HTTP 303 See Other
A redirect telling the client to fetch the result from another URL with GET — used after a form POST so refreshing doesn’t resubm…
400 Bad Request: The plain HTTP request was sent to HTTPS port (Nginx 497)
Plain http:// traffic arrived on a port Nginx expects to be TLS (443 or a custom SSL port).
WordPress: ERR_TOO_MANY_REDIRECTS / redirected you too many times on wp-admin or the whole site
WordPress and the server/proxy keep redirecting to each other — usually siteurl/home mismatch (http vs https, www vs non-www) or…
HTTP 301 Moved Permanently
The resource has a new permanent URL; clients and search engines should use the address in the Location header from now on.
CLEARTEXT communication to host not permitted by network security policy
Android 9+ blocks plain `http://` requests by default; the app tried to call a non-HTTPS URL.
Unable to configure HTTPS endpoint. No server certificate was specified, and the default developer certificate could not be found or is out of date
Kestrel was told to listen on HTTPS but has no certificate — the ASP.NET Core dev certificate is missing/expired, or production d…
HTTP 308 Permanent Redirect
A permanent redirect that, unlike 301, guarantees the method and body are kept.
App Transport Security has blocked a cleartext HTTP resource load
iOS blocked an `http://` request (or a weak-TLS HTTPS one) because App Transport Security requires secure connections.
Two steps away (33)
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
SyntaxError: Unexpected token < in JSON at position 0
`JSON.parse()` / `response.json()` received something that isn’t JSON — very often an HTML error page.
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…
HTTP 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
SSL: CERTIFICATE_VERIFY_FAILED / unable to get local issuer certificate
The client couldn’t verify the server’s TLS certificate chain, so it refused the HTTPS connection.
Cloudflare Error 525: SSL Handshake Failed
Cloudflare couldn’t complete a TLS handshake with your origin (SSL mode Full / Full strict).
ERR_SSL_VERSION_OR_CIPHER_MISMATCH on a Cloudflare site (certificate not issued / multi-level subdomain)
Cloudflare has no edge certificate for the hostname — the Universal SSL cert is still pending, or the hostname is a second-level…
NET::ERR_CERT_AUTHORITY_INVALID with a Cloudflare Origin Certificate (record not proxied)
Cloudflare Origin CA certificates are only trusted by Cloudflare — visitors reaching the origin directly (grey-cloud record, dire…
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…
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…
fatal: Authentication failed for 'https://github.com/x/y.git/'
HTTPS authentication to the Git host failed — wrong or expired credentials, or a password used where a token is required.
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.
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…
ERR_CACHE_MISS: Confirm Form Resubmission
You pressed Back/Refresh on a page that was the result of a form POST, so the browser asks before sending the form again.
HTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
FastCGI sent in stderr: "Primary script unknown"
Nginx passed a script path to PHP-FPM that PHP-FPM couldn’t find — usually a wrong SCRIPT_FILENAME or root.
Nginx 444 No Response (connection closed without response)
An Nginx-specific code: the server deliberately closed the connection without sending anything — a rule is dropping the request.
WordPress login: Error: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.
WordPress’s test cookie wasn’t returned on login — often a siteurl/home or domain mismatch, caching of wp-login.php, or headers a…
Elementor: The preview could not be loaded / Server Error 500 / Preview Debug
Elementor’s editor couldn’t load the page preview in its iframe — PHP errors, memory limits, mixed URLs, or plugin conflicts.
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 410 Gone
The resource used to exist but was intentionally and permanently removed, with no forwarding address.
Cloudflare Error 520: Web Server Returned an Unknown Error
Cloudflare connected to your origin, but the origin returned an empty, unknown or invalid response.
remote: Support for password authentication was removed on August 13, 2021. Please use a personal access token instead.
GitHub no longer accepts account passwords for Git over HTTPS.
fatal: unable to access 'https://…': SSL certificate problem: unable to get local issuer certificate
Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.
SSL error: tlsv1 alert protocol version / unsupported protocol / no protocols available
The client and server couldn’t agree on a TLS version or cipher, so the HTTPS handshake failed before any HTTP was exchanged.
System.IO.IOException: Failed to bind to address http://127.0.0.1:5000: address already in use
Kestrel can’t listen because another process (often a previous run of the same app) uses the port.
HttpRequestException: The SSL connection could not be established, see inner exception. (AuthenticationException: The remote certificate is invalid)
HttpClient couldn’t complete the TLS handshake — untrusted/self-signed certificate, name mismatch, expired certificate, or TLS ve…
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.
Firefox: The page isn’t redirecting properly — Firefox has detected that the server is redirecting the request in a way that will never complete
Firefox's wording for a redirect loop (Chrome calls it ERR_TOO_MANY_REDIRECTS).
NSUnknownKeyException: this class is not key value coding-compliant for the key x
A storyboard/XIB has a connection to an outlet or action that no longer exists in the class (renamed or deleted), or the view’s c…
unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard
The table/collection view was asked for a reusable cell identifier that was never registered.
Auto Layout: Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want
Two or more Auto Layout constraints conflict; UIKit breaks one to recover and logs this message.
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