Error map
Unable to configure HTTPS endpoint Unable to configure HTTPS endpoint. No server certificate was specified, and the default developer certificate could not be found or is out of date
.NET · layer 4, Application & API
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)
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Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.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.
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…
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.
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 307 Temporary Redirect
A temporary redirect that keeps the original method and body — a POST stays a POST at the new URL.
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).
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.
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.
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…
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.
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)
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.
javax.net.ssl.SSLHandshakeException: PKIX path building failed: unable to find valid certification path to requested target
Java doesn’t trust the server’s certificate chain (self-signed, corporate proxy CA, or missing intermediate).
Error [ERR_TLS_CERT_ALTNAME_INVALID]: Hostname/IP does not match certificate's altnames
The server’s certificate doesn’t cover the hostname you connected to.
Error: connect ECONNREFUSED 127.0.0.1:5432
Nothing is listening at that host:port — the target service is down or you’re connecting to the wrong address.
HTTP 407 Proxy Authentication Required
A proxy between you and the server requires credentials before it will forward your request.
HTTP 408 Request Timeout
The server closed the connection because the client took too long to send the complete request.
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.
Cloudflare Error 525: SSL Handshake Failed
Cloudflare couldn’t complete a TLS handshake with your origin (SSL mode Full / Full strict).
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…
Cloudflare Error 520: Web Server Returned an Unknown Error
Cloudflare connected to your origin, but the origin returned an empty, unknown or invalid response.
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.
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…
SecurityError: Blocked a frame with origin "x" from accessing a cross-origin frame.
Script tried to read or modify an iframe (or window) from another origin.
Refused to load the script because it violates the following Content Security Policy directive
The page’s Content-Security-Policy doesn’t allow that script, style, image or connection source.
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.
HTTP 302 Found (Temporary Redirect)
The resource is temporarily at another URL; clients should keep using the original URL for future requests.
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…
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.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
Docker: Bind for 0.0.0.0:80 failed: port is already allocated
Another container or host process already publishes that host port.
Web server failed to start. Port 8080 was already in use.
Spring Boot couldn’t bind its embedded server port because another process uses it.
Git: Permission denied (publickey). fatal: Could not read from remote repository.
SSH authentication to GitHub/GitLab/Bitbucket failed — no key, wrong key, or the key isn’t added to your account.
Azure AD (Entra ID): AADSTS700016 Application not found in the directory
The client ID in your sign-in request doesn’t exist in the tenant you’re authenticating against.
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
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.
NET::ERR_CERT_DATE_INVALID (certificate expired)
The site’s certificate has expired (or isn’t valid yet) — or the device clock is wrong.
ERR_SSL_PROTOCOL_ERROR (This site can't provide a secure connection)
The browser couldn’t negotiate TLS — the server sent an invalid response, often plain HTTP on the HTTPS port.
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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