| SecurityError: Failed to read the 'localStorage' property |
Console: SecurityError: Failed to read the 'localStorage' property from 'Window': Access is denied for this document |
The page cannot use `localStorage` because cookies/site data are blocked, it runs in a sandboxed iframe, or t… |
| ERR_CONNECTION_TIMED_OUT |
ERR_CONNECTION_TIMED_OUT: This site can’t be reached — example.com took too long to respond |
The browser waited for the server but got no response — the server is down/unreachable, a firewall drops traf… |
| ERR_TUNNEL_CONNECTION_FAILED |
Chrome: No internet — There is something wrong with the proxy server. ERR_TUNNEL_CONNECTION_FAILED |
Chrome asked a proxy to open a tunnel (HTTPS CONNECT) to the website and the proxy refused or could not reach… |
| ERR_TOO_MANY_REDIRECTS |
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. |
| Geolocation permission denied |
Console: User denied Geolocation / Only secure origins are allowed (geolocation) / GeolocationPositionError code 1 |
`navigator.geolocation` failed because the user blocked location, the page is not on HTTPS, or the OS has loc… |
| ERR_CONNECTION_RESET |
ERR_CONNECTION_RESET: This site can’t be reached — The connection was reset |
The connection to the website was cut off mid-way — by the server, a firewall/antivirus, a VPN/proxy, or netw… |
| DNS_PROBE_FINISHED_NXDOMAIN |
Chrome: This site can’t be reached — server IP address could not be found. DNS_PROBE_FINISHED_NXDOMAIN |
The DNS server answered that the domain name does not exist (NXDOMAIN) — a typo, an expired or unregistered d… |
| The page isn’t redirecting properly |
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). |
| A TLS error caused the secure connection to fail |
Safari: Safari Can’t Open the Page — A TLS error caused the secure connection to fail |
Safari could not set up a secure TLS connection — an expired or untrusted certificate, an outdated server con… |
| ERR_EMPTY_RESPONSE |
Chrome: This page isn’t working — example.com didn’t send any data. ERR_EMPTY_RESPONSE |
The server accepted the connection but closed it without sending any HTTP response — a crash, timeout or misc… |
| Unchecked runtime.lastError |
Console: Unchecked runtime.lastError: The message port closed before a response was received (extension message) |
A browser extension sent or received a message and the other side closed the channel without replying — almos… |
| ERR_ADDRESS_UNREACHABLE |
Chrome: This site can’t be reached — The webpage at https://… might be temporarily down. ERR_ADDRESS_UNREACHABLE |
The computer has no route to the server’s IP address — often an IPv6 problem, a wrong local-network address,… |
| NET::ERR_CERT_REVOKED |
Chrome: Your connection is not private — NET::ERR_CERT_REVOKED (the certificate was revoked) |
The site’s TLS certificate has been revoked by the certificate authority, so browsers refuse to trust it. |
| ERR_SSL_OBSOLETE_VERSION |
Chrome: Connection not secure — ERR_SSL_OBSOLETE_VERSION (old TLS 1.0/1.1) |
The server only supports an outdated TLS version that current browsers no longer allow. |
| DNS_PROBE_FINISHED_NO_INTERNET |
Chrome: No internet — DNS_PROBE_FINISHED_NO_INTERNET (DNS probe finished, no internet) |
Chrome’s built-in DNS probe could not reach any DNS server, so the device effectively has no working internet… |
| Page Unresponsive |
Chrome: Page Unresponsive — The following page(s) have become unresponsive. You can wait for them to become responsive or exit the page(s) |
A tab is stuck in a busy loop or waiting on something heavy, so Chrome offers to wait or kill it. |
| ERR_NETWORK_ACCESS_DENIED |
Chrome: This site can’t be reached — ERR_NETWORK_ACCESS_DENIED (blocked by firewall or antivirus) |
Something on your computer — usually the Windows firewall or antivirus — denied Chrome network access. |
| ERR_CONNECTION_CLOSED |
Chrome: This site can’t be reached — example.com unexpectedly closed the connection. ERR_CONNECTION_CLOSED |
The server closed the connection before finishing the TLS handshake or sending a response — typical for HTTP/… |
| Uncaught (in promise) |
Console: Uncaught (in promise) Error / TypeError / DOMException — unhandled promise rejection |
A promise was rejected and no `.catch()` or `try/catch` handled it, so the browser logs it as an unhandled re… |
| ERR_CONNECTION_ABORTED |
Chrome: The connection was aborted — ERR_CONNECTION_ABORTED (software on your computer caused it) |
The connection was aborted on your own computer — usually antivirus, a firewall or VPN software terminating i… |
| Extension context invalidated |
Console: Uncaught Error: Extension context invalidated (extension was updated or reloaded) |
A content script from an extension kept running after the extension was reloaded, updated or removed, so its… |
| Failed to execute on 'Node' |
Console: Uncaught TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node' |
A DOM method received something that is not a DOM node — `null`, `undefined`, a string, or a jQuery/React obj… |
| VersionError |
Console: VersionError: The requested version (1) is less than the existing version (2) — IndexedDB open() failed |
`indexedDB.open(name, version)` was called with a lower version number than the database already has. |
| ERR_CACHE_MISS |
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… |
| SSL_ERROR_NO_CYPHER_OVERLAP |
Firefox: Secure Connection Failed — SSL_ERROR_NO_CYPHER_OVERLAP (no common cipher) |
Firefox and the server share no TLS cipher suite, so the secure handshake cannot even start. |
| net::ERR_FAILED |
Chrome DevTools: net::ERR_FAILED — a request failed with no specific reason (CORS, extension, mixed content or network) |
ERR_FAILED is Chrome’s catch-all for a failed request. In DevTools it very often hides a CORS rejection, an e… |
| ERR_INTERNET_DISCONNECTED |
Chrome: No internet — ERR_INTERNET_DISCONNECTED (You are not connected to the internet) |
Chrome sees no working network connection on the device, so it cannot load any page. |
| HSTS |
Chrome: You cannot visit example.com right now because the website uses HSTS (NET::ERR_CERT_… no bypass) |
The site told browsers to use only valid HTTPS (HSTS), so Chrome hides the "Proceed anyway" link when its cer… |
| ERR_NETWORK_CHANGED |
Chrome: Your connection was interrupted — A network change was detected. ERR_NETWORK_CHANGED |
The device switched networks (Wi-Fi to mobile data, VPN on/off, IP renewed) while the page was loading, so th… |
| Refused to display in a frame |
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-ances… |
| Server not found |
Firefox: Hmm. We’re having trouble finding that site. / Server not found (DNS_PROBE or NS_ERROR_UNKNOWN_HOST) |
Firefox could not resolve the website’s hostname to an IP address — a typo, a DNS problem or no internet. |
| Aw, Snap! |
Chrome: Aw, Snap! Something went wrong while displaying this webpage. Error code: STATUS_ACCESS_VIOLATION / SIGILL / Out of Memory |
A Chrome tab crashed — out of memory, a faulty extension, a graphics/driver issue or a very heavy page. |
| Failed to execute postMessage |
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, s… |
| NotAllowedError: Permission denied |
Console: NotAllowedError: Permission denied (getUserMedia — camera or microphone blocked) |
The user (or the browser/OS/policy) denied camera or microphone access, so `navigator.mediaDevices.getUserMed… |
| The canvas has been tainted by cross-origin data |
Console: SecurityError: Failed to execute 'toDataURL' / 'getImageData' on 'HTMLCanvasElement': Tainted canvases may not be exported |
You drew an image from another origin onto a canvas without CORS permission, so the browser blocks reading pi… |
| ERR_CONTENT_DECODING_FAILED |
Chrome: This page isn’t working — sent an invalid response. ERR_CONTENT_DECODING_FAILED |
The response claims to be compressed (gzip/brotli) but cannot be decompressed — it was double-compressed, tru… |
| ERR_QUIC_PROTOCOL_ERROR |
Chrome: This site can’t be reached — ERR_QUIC_PROTOCOL_ERROR (HTTP/3 over UDP blocked) |
Chrome tried HTTP/3 (QUIC over UDP) and the connection failed — usually a firewall, VPN or proxy that blocks… |
| ERR_SSL_VERSION_OR_CIPHER_MISMATCH |
Chrome: This site can’t provide a secure connection — uses an unsupported protocol. ERR_SSL_VERSION_OR_CIPHER_MISMATCH |
The browser and the server could not agree on a TLS version or cipher — the server is too old or misconfigure… |
| ERR_PROXY_CONNECTION_FAILED |
Chrome: Unable to connect to the proxy server. ERR_PROXY_CONNECTION_FAILED |
Chrome is configured to use a proxy but cannot connect to it — the proxy is down or the setting is wrong (oft… |
| Failed to find a valid digest in the 'integrity' attribute |
Console: Failed to find a valid digest in the 'integrity' attribute for resource … with computed SHA-256 integrity |
A `` or `` with an `integrity` hash was blocked because the downloaded file does not match that hash. |
| NotFoundError: Requested device not found |
Console: NotFoundError: Requested device not found (getUserMedia has no camera or microphone) |
`getUserMedia` found no camera or microphone matching the constraints — the device is missing, disabled or th… |
| NotReadableError: Could not start video source |
Console: NotReadableError: Could not start video source (camera in use by another app) |
The camera or microphone exists but could not be opened — another application, tab or a driver problem holds… |
| SEC_ERROR_UNKNOWN_ISSUER |
Firefox: Warning: Potential Security Risk Ahead — SEC_ERROR_UNKNOWN_ISSUER (certificate not trusted) |
Firefox does not trust the authority that issued the site's certificate — a self-signed certificate, a missin… |
| net::ERR_CONTENT_LENGTH_MISMATCH |
Chrome DevTools: net::ERR_CONTENT_LENGTH_MISMATCH — body shorter than the Content-Length header |
The server promised a number of bytes in `Content-Length` and sent a different number, so Chrome treats the d… |
| ERR_HTTP2_PROTOCOL_ERROR |
Chrome: This page isn’t working — example.com is unable to handle this request. ERR_HTTP2_PROTOCOL_ERROR |
The HTTP/2 connection broke a protocol rule — a server, proxy or CDN sent an invalid or oversized frame/heade… |
| Permissions policy violation |
Console: [Violation] Permissions policy violation: camera is not allowed in this document (Feature-Policy) |
A browser feature (camera, microphone, geolocation, fullscreen, payment…) was blocked by a `Permissions-Polic… |
| Refused to apply style from |
Console: Refused to apply style from 'https://…/style.css' because its MIME type ('text/html') is not a supported stylesheet MIME type |
The stylesheet URL returned something that is not CSS — usually a 404/HTML error page — and `X-Content-Type-O… |
| Safari can’t find the server |
Safari: Safari Can’t Open the Page because Safari can’t find the server |
Safari could not resolve the hostname — a typo, DNS trouble or no internet connection. |
| captive portal |
Browser: This network requires you to sign in — captive portal (hotel, airport, café Wi-Fi) blocking HTTPS sites |
The Wi-Fi needs a login or acceptance page first; until you complete it, secure sites fail with certificate o… |
| net::ERR_INCOMPLETE_CHUNKED_ENCODING |
Chrome DevTools: net::ERR_INCOMPLETE_CHUNKED_ENCODING 200 (OK) — response cut off midway |
The server started sending a chunked response with status 200 and then stopped before the final chunk, so Chr… |
| $ is not defined |
Console: Uncaught ReferenceError: $ is not defined (jQuery not loaded or loaded after your code) |
Your code uses jQuery's `$` before jQuery has loaded — the script is missing, blocked, in the wrong order, or… |
| DevTools failed to load source map |
DevTools: Failed to load source map — Could not load content for https://…/app.js.map: HTTP error: status code 404 |
DevTools could not download the `.map` file that a script or stylesheet points to, so you see minified code i… |
| Service worker registration failed |
Console: Failed to register a ServiceWorker: A bad HTTP response code (404) was received when fetching the script |
The browser could not fetch, parse or install the service worker script, or the page is not allowed to regist… |