This page is about Caddy 1 and will stay here forever.

User Guide


Provides a directive to filter response bodies. This could be useful to modify static HTML files to add (for example) Google Analytics source code to it.

Full documentation


filter rule { path <regexp pattern> content_type <regexp pattern> path_content_type_combination <and|or> search_pattern <regexp pattern> replacement <replacement pattern> } filter rule ... filter max_buffer_size <maximum buffer size in bytes>
  • rule: Defines a new filter rule for a file to respond. Important: Define path and/or content_type not to open. Slack rules could dramatically impact the system performance because every response is recorded to memory before returning it.
    • path: Regular expression that matches the requested path.
    • content_type: Regular expression that matches the requested content type that results after the evaluation of the whole request.
    • path_content_type_combination: (Since 0.8) Could be and or or. (Default: and - before this parameter existed it was or)
    • search_pattern: Regular expression to find in the response body to replace it.
    • replacement: Pattern to replace the search_pattern with. &lt;br&gt;You can use parameters. Each parameter must be formatted like: {name}.
      • Regex group: Every group of the search_pattern could be addressed with {index}.
        • Example: &#34;My name is (.*?) (.*?).&#34; =&gt; &#34;Name: {2}, {1}.&#34;
      • Request context: Parameters like URL … could be accessed. &lt;br&gt;Example: Host: {request_host}
        • request_header_&lt;header name&gt;: Contains a header value of the request, if provided or empty.
        • request_url: Full requested url
        • request_path: Requested path
        • request_method: Used method
        • request_host: Target host
        • request_proto: Used proto
        • request_proto: Used proto
        • request_remoteAddress: Remote address of the calling client
        • response_header_&lt;header name&gt;: Contains a header value of the response, if provided or empty.
      • Replacements in files: If the replacement is prefixed with a @ character it will be tried to find a file with this name and load the replacement from there. This will help you to also add replacements with larger payloads which will be ugly direct within the Caddyfile.
        • Example: @myfile.html
  • max_buffer_size: Limit the buffer size to the specified maximum number of bytes. If a rules matches the whole body will be recorded at first to memory before delivery to HTTP client. If this limit is reached no filtering will executed and the content is directly forwarded to the client to prevent memory overload. Default is: 10485760 (=10 MB)
Insert server name in every HTML page.
filter rule { content_type text/html.* search_pattern Server replacement "This site was provided by {response_header_Server}" }
Add Google Analytics to every HTML page from a file.
filter rule { path .*\.html search_pattern </title> replacement @googleAnalyticsSnippet.html }
Replace in every text file Foo with Bar.
filter rule { path .*\.txt search_pattern Foo replacement Bar }
Related Links

Access the full documentation for this plugin off-site:

Plugin Help

Get help from the maintainers of the http.filter plugin:

Plugin Website

Visit http.filter's website for more information:

Plugin Author: Gregor Noczinski
Last Updated: 14 Jul 2018, 8:09 AM
This plugin is independent of the Caddy project and is not endorsed or maintained by Caddy developers. Use at your own risk. Do not file issues for this plugin on Caddy's bug tracker.