Traefik Body Rewrite Plugin

Plugin Name: body-rewrite
Compatible with: Traefik v3
Purpose: Rewrites HTTP response bodies dynamically based on request headers using regex(Golang based) patterns. Supports gzip-compressed responses and multiple replacements per response. In fact, this plug-in works like a sub_filter in Nginx.

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✨ Features

• 🔄 Replace one or multiple occurrences in the response body using regex.
• 📦 Support for gzip-compressed responses.
• 📝 Use any header value as a dynamic replacement in the body.
• 🐛 Debug logging for troubleshooting.
• 💡 Works on JSON, HTML, or plain text bodies.

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⚙️ Configuration

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http:
  middlewares:
    rewrite-json:
      plugin:
        body-rewrite:
          headerName: "Origin"                              # Header to read replacement value from
          replacementPattern: "https://origin(/[^\"\\s]*)"  # Regex pattern to match in body
          replacement: "{header}$1"                         # Replacement string, {header} is replaced with header value
          debug: true                                       # Enable debug logging (optional)

Parameter	Type	Required	Description
headerName	string	✅	Name of the HTTP header whose value will be used in replacements.
replacementPattern	string	✅	Regex pattern to search in the body. Supports capture groups.
replacement	string	✅	Replacement string. Use {header} to insert the header value dynamically.
debug	boolean	❌	Enables debug logging (default: false).

📖 Example

Backend Response:

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{
  "logo": "https://origin/images/logo.png",
  "background": "https://origin/images/bg.png"
}

Request:

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curl -H "Origin: https://cdn.example.com" http://localhost/

Rewritten Response:

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{
  "logo": "https://cdn.example.com/images/logo.png",
  "background": "https://cdn.example.com/images/bg.png"
}

📝 Notes

If the specified header is missing, the body is returned unmodified.

Regex should account for line breaks if matching JSON (e.g. https://origin(/[^"\s]*)).

Regex based on Golang Regexp syntax.

Plugin can rewrite multiple occurrences of the pattern in a single response.