Error map
SameSite cookie blocked This Set-Cookie was blocked because it had the "SameSite=Lax" attribute but came from a cross-site response / SameSite=None requires Secure
Authentication · 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)
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…
Passport.js: Error: Failed to serialize user into session
Passport logged a user in but there’s no serializeUser function (or it didn’t call done), so the session can’t store the user.
Error: A cross-origin error was thrown. React doesn't have access to the actual error object in development.
An error happened in a script loaded from another origin, so the browser hid the details from React.
AWS: ExpiredToken — The security token included in the request is expired
Temporary AWS credentials (STS/SSO/assumed role) have expired.
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.
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…
OIDC Error: login_required / interaction_required / consent_required (silent authentication failed)
A silent sign-in (prompt=none, iframe or refresh) couldn’t complete because the user must interact — no session, consent needed,…
OAuth callback error: state mismatch / Unable to verify authorization request state / State cookie was missing
The state value returned to the callback doesn’t match what the app stored before redirecting — the CSRF protection for OAuth fai…
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.
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.
Script error. (at line 0) — cross-origin error details hidden
An error happened in a script from another origin, and the browser hid the details.
HTTP 431 Request Header Fields Too Large
The request headers — almost always cookies — exceed the server’s size limit.
Two steps away (32)
AWS S3: AccessDenied (403) when calling GetObject / PutObject
An IAM policy, bucket policy, ACL/ownership setting, Block Public Access or KMS key policy denied the S3 request.
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
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…
Warning: session_start(): Session cannot be started after headers have already been sent
session_start() ran after output was sent, so PHP can’t set the session cookie.
InvalidOperationException: Session has not been configured for this application or request
Code used HttpContext.Session, but session services/middleware aren’t registered — or UseSession runs after the endpoint that nee…
ForbiddenError: invalid csrf token (EBADCSRFTOKEN)
The request’s CSRF token is missing or doesn’t match the token tied to the user’s session/cookie.
Error: Minified React error #31; visit https://react.dev/errors/31 for the full message
A production React build threw an error whose message was shortened to a number.
kubectl: The connection to the server localhost:8080 was refused — did you specify the right host or port?
kubectl has no usable kubeconfig, so it falls back to localhost:8080 — or the cluster API server is unreachable.
AWS: Unable to locate credentials / Could not load credentials from any providers
The AWS CLI/SDK found no credentials in any place it looks — env vars, profile files, SSO cache or an instance/task role.
AWS: SignatureDoesNotMatch / InvalidClientTokenId — the request signature we calculated does not match
AWS rejected the request signature — wrong secret key, wrong region, clock skew, or a presigned URL used differently from how it…
Warning: Cannot modify header information - headers already sent
You called `header()`, `setcookie()` or `session_start()` after output had already been sent to the browser.
HTTP 411 Length Required
The server refuses a request with a body but no Content-Length header.
HTTP 428 Precondition Required
The server requires a conditional request (If-Match / If-Unmodified-Since) to prevent lost updates, and you didn’t send one.
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…
WordPress: 404 Not Found on every page except the homepage (permalinks / .htaccess / Nginx rules)
Pretty permalinks aren’t being routed to index.php — .htaccess is missing/ignored (Apache) or Nginx lacks try_files.
WordPress: 403 Forbidden on wp-admin, wp-login.php or admin-ajax.php
The server or a security layer refused access to WordPress admin URLs — file permissions, a security plugin/WAF rule, ModSecurity…
OAuth 2.0 Error: invalid_grant
The authorization code, refresh token or credentials sent to the token endpoint are invalid, expired, already used or were issued…
Warning: session_start(): open(/var/lib/php/sessions/sess_x, O_RDWR) failed: Permission denied
PHP can’t write session files to the configured session.save_path.
OAuth 2.0 Error: access_denied (The user or authorization server denied the request)
The authorization request was refused — the user clicked Cancel/Deny on the consent screen, or a policy denied access.
Laravel: 419 Page Expired (CSRF token mismatch)
Laravel rejected a POST because the CSRF token was missing, expired or didn’t match the session.
Forbidden (403) CSRF verification failed. Request aborted.
Django rejected a POST because the CSRF token was missing, wrong, or the request origin isn’t trusted.
OAuth PKCE error: invalid_grant — PKCE verification failed / code_verifier does not match code_challenge / code_challenge required
The code_verifier sent to the token endpoint doesn’t match the code_challenge from the authorize request, or PKCE is required but…
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…
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.
AbortError: The user aborted a request. / signal is aborted without reason
A fetch was cancelled through an AbortController (or the browser cancelled it).
TypeError: Failed to execute 'json' on 'Response': body stream already read
A fetch Response body was consumed twice (e.g. calling .text() then .json()).
Console: Refused to display 'https://…' in a frame because it set 'X-Frame-Options' to 'deny' / 'sameorigin'
The page you tried to embed in an `` forbids framing through the `X-Frame-Options` header or CSP `frame-ancestors`.
Console: Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://a.com') does not match the recipient window's origin ('https://b.com')
`window.postMessage()` was sent with a `targetOrigin` that differs from the receiving window's real origin, so the message is dro…
HTTP 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
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.
HTTP 414 URI Too Long
The request URL (usually the query string) is longer than the server will accept.
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