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Overview

The block responder immediately blocks requests with a 403 Forbidden status code. This is the most straightforward way to deny access to specific IP ranges.
The block responder requires no additional configuration beyond specifying the IP ranges.

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When to Use

Use the block responder when:
  • You want to explicitly deny access to certain IP ranges
  • A clear 403 Forbidden response is acceptable
  • You don’t need custom messages or status codes
  • You want a simple, no-configuration solution

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Configuration Examples

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Example 1: Block Specific IP Ranges

localhost:8080 {
    defender block {
        ranges 203.0.113.0/24 openai 198.51.100.0/24
    }
    respond "Human-friendly content"
}
This example blocks requests from:
  • The 203.0.113.0/24 CIDR range
  • All OpenAI IP addresses (using the built-in openai range)
  • The 198.51.100.0/24 CIDR range

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Example 2: Block Private Networks

{
    auto_https off
    order defender after header
    debug
}

:80 {
    bind 127.0.0.1 ::1

    defender block {
        ranges private
    }
    respond "This is what a human sees"
}

:83 {
    bind 127.0.0.1 ::1
    respond "Clear text HTTP"
}
This configuration:
  • Blocks all private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
  • Only serves content to public IP addresses
  • Useful for preventing internal network access

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Response Behavior

When a request is blocked:
  • HTTP status code: 403 Forbidden
  • Response body: Default Caddy 403 error page
  • Connection: Closed after response is sent
For custom error messages or status codes, use the custom responder instead.

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