Nginx Multiple Conditional Test

Luke Hebert

- 2 minutes read - 320 words

Nginx does not support compound boolean expressions inside a single if block, so you often need to chain multiple if statements to build a decision. The trick is to accumulate a value into a variable across several conditions, then test that variable once at the end.

Building a Composite Variable

The example below checks three conditions in sequence. Each one appends a letter to $test when its condition is true:

if ($request_uri = /) {
    set $test "A";
}

if ($host ~* teambox.com) {
    set $test "${test}B";
}

if ($http_cookie !~* "auth_token") {
    set $test "${test}C";
}

After all three blocks run, $test holds a string like ABC, BC, or C depending on which conditions matched.

Routing on the Combined Result

Once the variable is assembled, a final if block performs the actual routing decision:

if ($test = ABC) {
    proxy_pass http://teambox-cms.heroku.com;
    break;
}

The break directive is important here. It tells Nginx to stop processing further if blocks in the current context and use the proxy_pass that was just set. Without it, a later if could overwrite the upstream.

Things to Keep in Mind

Warning

Nginx if directives are notoriously tricky. The official docs call them “evil” for a reason. Stick to simple equality or regex tests, avoid nesting if blocks, and always pair proxy_pass with break to prevent unexpected overrides.

A few practical tips:

  • Use set (not rewrite ... last) when you only need to store a value.
  • Quote your variable expansions ("${test}B") so Nginx does not misparse the string.
  • Test your configuration with nginx -t before reloading.
  • If the logic grows beyond three or four conditions, consider moving the decision into a Lua script via lua-nginx-module for cleaner, more maintainable code.

This pattern is especially handy when you need to combine a URI check, a host check, and a cookie check into a single routing rule without writing a separate server block for every combination.