Why the Trailing Slash Matters in Nginx proxy_pass and location Directives

Background

Nginx is a lightweight, high‑performance web server widely used by large Chinese internet companies such as Baidu, Alibaba, Tencent, Toutiao, Meituan and Didi. Because its configuration is critical, a missing “/” in a proxy_pass directive can cause access errors, which this article investigates.

Detailed Explanation of location Matching

Each location block matches a request URI. Nginx parses the request path from top to bottom and applies the first matching block.

Example configuration for the request http://www.wandouduoduo.com/wddd/index.html:

location /wddd/  {
    proxy_connect_timeout 18000;
    proxy_send_timeout 18000;
    proxy_read_timeout 18000;
    proxy_pass http://127.0.0.1:8080;
}

When this location matches, the request is proxied to the local Tomcat service on port 8080, which returns the response.

Summary: If a location ends with “/”, it matches the exact directory; without “/”, it performs a prefix (fuzzy) match.

For example, location /wandou matches /wandou, /wandouduoduo, etc., while location /wandou/ matches only the exact /wandou/ path.

Four Cases of proxy_pass with and without “/”

All requests use the same base URL http://www.wandouduoduo.com/wddd/index.html and match the /wddd/ location.

Case 1: With “/”

location /wddd/ {
    proxy_pass http://127.0.0.1:8080/;
}

Result: request is proxied to http://127.0.0.1:8080/index.html.

Case 2: Without “/”

location /wddd/ {
    proxy_pass http://127.0.0.1:8080;
}

Result: request is proxied to http://127.0.0.1:8080/wddd/index.html.

Case 3: Adding a directory with “/”

location /wddd/ {
    proxy_pass http://127.0.0.1:8080/sun/;
}

Result: request is proxied to http://127.0.0.1:8080/sun/index.html.

Case 4: Adding a directory without “/”

location /wddd/ {
    proxy_pass http://127.0.0.1:8080/sun;
}

Result: request is proxied to http://127.0.0.1:8080/sunindex.html (missing slash).

Conclusion

Appending “/” to a location makes it match only the exact directory, while omitting it allows prefix matching. For proxy_pass, the presence or absence of a trailing slash determines how the upstream URL is concatenated.

Try the following configuration to experiment:

server {
  listen 80;
  server_name localhost;

  location /wddd01/ {
    proxy_pass http://localhost:8080;
  }

  location /wddd02/ {
    proxy_pass http://localhost:8080/;
  }

  location /wddd03 {
    proxy_pass http://localhost:8080;
  }

  location /wddd04 {
    proxy_pass http://localhost:8080/;
  }

  location /wddd05/ {
    proxy_pass http://localhost:8080/haha;
  }

  location /wddd06/ {
    proxy_pass http://localhost:8080/haha/;
  }

  location /wddd07 {
    proxy_pass http://localhost:8080/haha;
  }

  location /wddd08 {
    proxy_pass http://localhost:8080/haha/;
  }
}