Error map
ATS App Transport Security has blocked a cleartext HTTP resource load
iOS · layer 1, On your device
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Git doesn’t trust the HTTPS server’s certificate — corporate proxy, self-hosted Git with an internal CA, or outdated CA bundle.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.
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.
Error Domain=NSURLErrorDomain Code=-1009 "The Internet connection appears to be offline."
URLSession couldn’t reach the network — the device is offline, the app’s cellular data is disabled, or the simulator lost network…
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).
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.
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.
Two steps away (36)
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.
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.
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.
remote: Repository not found. fatal: repository 'https://github.com/x/y.git/' not found
GitHub/GitLab says the repository doesn’t exist — or you lack access to a private repo.
Host key verification failed. fatal: Could not read from remote repository.
SSH doesn’t trust the server’s host key — first connection in a non-interactive environment, or the key changed.
ECS task stopped: CannotPullContainerError: pull image manifest has been retried ... / ref pull has been retried
The ECS task couldn’t pull its image — no network route to the registry, missing ECR permissions, or a wrong image tag.
Error response from daemon: network X not found
The container or Compose project refers to a Docker network that doesn’t exist (any more).
Error response from daemon: Pool overlaps with other one on this address space
Docker tried to create a network whose subnet clashes with an existing Docker network (or a VPN/host route).
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.
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.
JWT Expired / Invalid Token
The JSON Web Token sent with the request is expired, malformed or signed with a different key, so the API rejects it (usually wit…
Thread 1: signal SIGABRT (app crashes with "libc++abi: terminating")
The app deliberately aborted — an uncaught exception, failed assertion or fatalError. The console above the crash has the real me…
Main Thread Checker: UI API called on a background thread: -[UIView setNeedsLayout]
UIKit was used from a background thread; UI must only be touched on the main thread.
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.
Swift: Could not cast value of type 'X' to 'Y'
A force cast (as!) failed because the object isn’t the expected type.
Building for iOS Simulator, but linking in object file built for iOS, for architecture arm64
A library contains device-only arm64 code; Apple Silicon simulators also run arm64 and need a separate simulator slice.
Unable to Install "App": This app cannot be installed because its integrity could not be verified
iOS rejected the app because its signature doesn’t validate for this device — expired/revoked certificate, ad-hoc profile without…
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