Error map
417 HTTP 417 Expectation Failed
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 400 Bad Request
The server could not understand the request because its syntax, headers or body are malformed or invalid.
Upload error: File too large (LIMIT_FILE_SIZE / file exceeds maximum upload size)
The uploaded file is larger than the limit set by the API, framework or server.
Cloudflare 413 Request Entity Too Large (upload over the plan limit)
The request body is larger than Cloudflare allows through the proxy — 100 MB on Free/Pro, 200 MB Business, 500 MB Enterprise defa…
WordPress: Sorry, you are not allowed to upload this file type / Sorry, this file type is not permitted for security reasons
WordPress blocked the upload because the file extension/MIME type isn’t in its allowed list (SVG, JSON, WEBP on old versions, fon…
HTTP 411 Length Required
The server refuses a request with a body but no Content-Length header.
Upload error: File type not allowed / unsupported file type
The upload was rejected because the file’s type — extension, MIME type or actual content — isn’t on the allowed list.
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 1040 / 1041: Invalid request header modification
A Transform Rule tried to set or remove a request header that Cloudflare doesn’t allow to be modified, or produced an invalid val…
Windows Update error 0x8024402C (cannot connect to update server)
Windows Update can’t reach Microsoft’s servers — a proxy, DNS, firewall or WSUS setting is blocking the connection.
Upload error: checksum mismatch (BadDigest / Content-MD5 did not match / XAmzContentSHA256Mismatch)
The server computed a different checksum for the data it received than the one your client declared, so it rejected the upload as…
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…
HTTP 511 Network Authentication Required
A captive portal (hotel, airport, office Wi-Fi) is intercepting your traffic until you log in or accept its terms.
Two steps away (36)
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
HTTP 405 Method Not Allowed
The URL exists, but it doesn’t accept the HTTP method you used (e.g. POST to a GET-only route).
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.
WordPress: The link you followed has expired
Usually an upload (theme, plugin, media) larger than PHP’s upload/post limits — WordPress receives an empty request and shows thi…
PHP upload error 1: The uploaded file exceeds the upload_max_filesize directive in php.ini
The uploaded file is bigger than PHP’s upload_max_filesize, so PHP discarded it.
API Error: Too many concurrent requests (concurrency limit reached)
You have more requests in flight at once than the API allows for your key — even if your requests-per-minute rate is fine.
Too many open files (EMFILE)
The process hit its file-descriptor limit — sockets, files and pipes all count.
S3 EntityTooLarge: Your proposed upload exceeds the maximum allowed size
A single PUT can be at most 5 GB (and presigned POST policies can set lower limits); larger files must use multipart upload.
Lambda: Request must be smaller than 6291456 bytes for the InvokeFunction operation (RequestEntityTooLargeException)
The event payload (or response) is over Lambda’s 6 MB synchronous limit (256 KB for async invocations).
NotAllowedError: play() failed because the user didn't interact with the document first.
The browser blocked media autoplay with sound until the user interacts with the page.
WordPress: Unable to create directory wp-content/uploads/2026/10. Is its parent directory writable by the server?
PHP can’t write to wp-content/uploads — wrong ownership/permissions, a wrong upload path, full disk, or open_basedir restrictions.
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…
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.
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.
Unexpected characters at the top of the page / headers already sent by BOM
A UTF-8 byte-order mark (BOM) at the start of a PHP file is sent as output, breaking headers, JSON and images.
HTTP 415 Unsupported Media Type
The server refuses the request because the body’s Content-Type isn’t one it accepts.
WordPress: Sorry, you are not allowed to access this page.
Your user role lacks the capability for that admin screen — or the database table prefix / user capabilities are out of sync afte…
API Error: Invalid type — expected integer, received string
A request field has the wrong data type — a string where the API expects a number, a number where it expects a boolean, an object…
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 505 HTTP Version Not Supported
The server doesn’t support the HTTP protocol version used in the request.
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.
HTTP 416 Range Not Satisfiable
The client asked for a byte range (Range: bytes=…) that lies outside the file — usually a resumed download of a file that changed…
Cloudflare Error 1035 / 1036: Invalid request rewrite (invalid URI path / query string)
A Transform Rule (URL rewrite) produced an invalid path or query string.
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.
npm ERR! code EINTEGRITY — sha512 integrity checksum failed
A downloaded package’s hash doesn’t match the integrity value in package-lock.json — a corrupted cache, a changed tarball, or a l…
API Error: Job / operation not found or expired (async task ID unknown)
The status URL or job ID for an asynchronous operation (export, import, render, batch) doesn’t exist any more, or never existed.
WordPress Media: “HTTP error.” when uploading images
The upload request failed on the server — memory or timeout during image processing, upload size limits, ModSecurity, or Imagick…
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 304 Not Modified
The cached copy is still valid, so the server sends no body and the client reuses its cache.
SyntaxError: Unexpected token < in JSON at position 0
`JSON.parse()` / `response.json()` received something that isn’t JSON — very often an HTML error page.
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…
Error: socket hang up / read ECONNRESET
The other side closed the TCP connection abruptly while your client was still using it.
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