ERR_INVALID_RESPONSE, what it means and how to fix it

Something answered your browser, but what it sent was not an HTTP response the browser could parse. The usual story is a mismatch: the address points at a service that is not a web server at all (a database port, a mail port, a game server), or the scheme and the server disagree, an https:// address aimed at a server that only speaks plain HTTP, or the reverse.

The fix, in order

  1. Check the scheme and port in the address. https:// against a plain-HTTP server (or http:// against an HTTPS-only port) is the most common cause. Match them: most dev servers are plain HTTP on their custom ports, so http://localhost:3000, not https.
  2. Confirm the port actually runs a web service. Browsing to a port that hosts something else (a database on 5432, SSH on 22) cannot work; the service answers in its own protocol and the browser reports it as invalid. This is expected, not a fault.
  3. If a proxy is configured, test without it. A broken or wrong-type proxy (an HTTP browser setting pointed at a SOCKS proxy, for instance) returns garbage the browser cannot parse. Settings → Network & internet → Proxy on Windows.
  4. For a public website that worked before, reload later and try another network; a misconfigured load balancer node can emit malformed responses until the operator pulls it.

If it is your own deployment

Check that the process behind the port is the web server you think it is (another service may have taken the port), that TLS termination happens where you expect (a proxy passing raw TLS to a plain-HTTP backend produces exactly this), and that the server is not emitting a broken status line or headers. curl -v against the address shows the raw first bytes, which settles what is actually being sent.

If it still happens

If the raw response begins with something that is plainly another protocol's greeting (an SSH or SMTP banner, a database handshake), the address is simply pointed at a non-web service, and no browser setting will ever make it load.

Common questions

Why does my browser show this for my router or printer admin page? Some embedded admin pages speak odd dialects of HTTP or sit behind redirects to non-standard ports. If the device's page works in one browser and not another, try its exact address including the port from the manual; the device is answering, just not in a dialect Chrome accepts.

Is ERR_INVALID_RESPONSE a security warning? Not as such; it means unparseable, not untrusted. But an intercepting portal or proxy that answers with its own content can produce it, so on an unfamiliar network treat it as one more reason to join the network properly or switch to one you trust.

Related errors

ERR_EMPTY_RESPONSE · ERR_SSL_PROTOCOL_ERROR · ERR_UNKNOWN_URL_SCHEME