When analyzing website performance using Google PageSpeed Insights, one common recommendation is to specify the character encoding early in HTTP headers. This helps browsers render content faster by eliminating the need to perform charset detection.

When examining the headers from your NGINX server:

Connection: keep-alive
Date: Fri, 16 Sep 2011 12:43:24 GMT
Last-Modified: Fri, 02 Sep 2011 15:13:17 GMT
Server: nginx/0.7.67

We notice the missing Content-Type header with charset specification, which explains why simply adding charset utf-8; in your server block didn't work as expected.

To correctly set the charset in HTTP headers, you need to modify the Content-Type header. Here's the proper way to configure it in your NGINX config file:

server {
    listen 80;
    server_name example.com;
    
    # Set charset for text/html and other text content types
    charset utf-8;
    charset_types text/html text/plain text/xml text/css text/javascript application/javascript application/x-javascript application/json;
    
    # Ensure Content-Type header includes charset
    add_header Content-Type "text/html; charset=utf-8";
    
    location / {
        try_files $uri $uri/ =404;
    }
}

The key directives in this configuration are:

• charset utf-8; - Sets the default charset for all text responses
• charset_types - Specifies which MIME types should have charset added
• add_header Content-Type - Explicitly sets the charset for HTML content

After implementing these changes, verify your headers using curl:

curl -I http://yourdomain.com

You should now see the proper charset declaration:

Content-Type: text/html; charset=utf-8

For more complex setups, you might want to:

1. Set different charsets for different content types
2. Conditionally add charset based on request headers
3. Handle legacy systems that might require different encodings

Here's an example of conditional charset handling:

location /legacy {
    charset windows-1251;
    charset_types text/html;
}

When analyzing website performance using tools like Google PageSpeed Insights, you might encounter recommendations to specify charset headers early. This is particularly important for HTML files, as it helps browsers correctly interpret character encoding before parsing the document.

Many developers attempt to set the charset by simply adding charset utf-8; in the server block, but this often doesn't work as expected. The server might still respond without the proper Content-Type header including charset information.

Here's the correct way to configure charset headers in NGINX:

server {
    listen 80;
    server_name example.com;
    
    # For HTML files
    location ~* \.html?$ {
        charset utf-8;
        add_header Content-Type "text/html; charset=utf-8";
    }
    
    # For other text files
    location ~* \.(css|js|json|xml)$ {
        charset utf-8;
        add_header Content-Type "text/$1; charset=utf-8";
    }
}

Another effective method is to set the default charset for all text responses:

http {
    charset utf-8;
    charset_types text/html text/css text/plain text/xml application/json application/javascript;
    ...
}

After implementing these changes, verify the headers using curl:

curl -I http://yourdomain.com/index.html

You should see output similar to:

HTTP/1.1 200 OK
Server: nginx/1.18.0
Date: Mon, 01 Nov 2021 12:00:00 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 1234
Connection: keep-alive
...

Setting charset headers properly can improve page rendering speed by:

• Eliminating the need for browsers to perform charset detection
• Preventing potential reflows when the correct charset is applied late
• Meeting Google PageSpeed recommendations for better SEO

If the charset header still doesn't appear:

1. Check for conflicting directives in other configuration files
2. Ensure you're not overriding Content-Type headers elsewhere
3. Verify that the file types are correctly matched in your location blocks
4. Remember to reload or restart NGINX after configuration changes