caddy2-filter

Replace text in HTTP response based on regex. Similar to http.filter in Caddy 1.

Usage

Only the listed fields are supported.

The replacement supports capturing groups of search_pattern (e.g. {1}) and caddy placeholders (e.g. {http.request.hostport})

Caddyfile:

# Add this block in top-level settings:
{
    order filter after encode
}

filter {
    # Only process URL matching this regex
    path <optional, regexp pattern, default: .*>
    # Don't process response body larger than this size
    max_size <optional, int, default: 2097152>
    search_pattern <regexp pattern>
    replacement <replacement string>
    # Only process content_type matching this regex
    content_type <regexp pattern>
}

# If you are using reverse_proxy, add this to its config to ensure
# reverse_proxy returns uncompressed body:

header_up -Accept-Encoding

JSON config (under apps › http › servers › routes › handle)

{
    "handler": "filter",
    "max_size": <int>,
    "path": "<regexp>",
    "search_pattern": "<regexp>",
    "replacement: "<string>",
    "content_type": "<regexp>"
}

Alternatives

As of Jun 2021, https://github.com/caddyserver/replace-response can achieve similar functionalities. This plugin's design differs from that one in the following aspects:

1. This plugin supports placeholders like {http.host}

2. This plugin allows capping the max size of buffered response

3. This plugin supports only replacing responses with certain content_types

4. replace-response supports stream mode, which features in better performance at the cost of possibilities of omitted replacements

5. replace-response is a semi-official plugin maintained by the same author of caddy