Nginx Config Check

Q: How do I validate config before reloading nginx?

Run nginx -t -c /etc/nginx/nginx.conf first; only when it prints syntax is ok / test is successful do nginx -s reload. Don't skip -t — a syntax error makes reload reject the new config while the old one keeps serving, which is easy to misread.

Q: What does unknown directive mean?

Usually a typo in the directive name or the module isn't loaded (e.g. the stream module isn't compiled in). Check nginx -V for --with-stream; recompile or use an equivalent config if missing.

Q: What is host not found in upstream?

nginx can't resolve a domain in an upstream block. Common when the upstream domain is misspelled, DNS is down, or you wrote an IP with a port in upstream. Confirm with dig, or use the IP directly.

Q: How do I fix bind() to 0.0.0.0:80 failed?

The port is in use. Run ss -tlnp | grep :80 to find the holder; often another nginx instance, Apache, or a previous process that didn't exit. Kill it or change the listen port.

Honest note: a browser cannot test the nginx config on your server. This tool generates the correct nginx -t command + common-error lookup — run it on your server for the real result. No fake "click-to-test" promise here.

Generate the test command

Enter a config path to get the test and dump commands.

Config file path

Common-error lookup

Error	Cause	Fix
`unknown directive`	Typo or module not loaded	Check spelling; `nginx -V` for the module compile flag
`directive is not allowed here`	Wrong context	http / server / location nesting — move to the right block
`host not found in upstream`	Upstream DNS resolution failed	`dig` to confirm; use the IP or fix DNS
`emerg bind() failed`	Port in use	`ss -tlnp \\| grep :80` to find the holder
`conflicting server name`	Duplicate server_name	Two server blocks share a name — merge or rename
`"upstream" directive is not allowed here`	Upstream in wrong block	upstream belongs at http level, not inside server

Nginx reverse proxy 502/504 troubleshooting — troubleshooting after a config change breaks

Nginx Config Check

Generate the test command

Common-error lookup

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