transform-encoding

Encoding transform

Last modified: 2026-04-27

Demonstrates the encoding transform. A static action returns a small JSON document; the transform converts the bytes to standard base64 via encoding: base64_encode. A response_modifier switches Content-Type to text/plain; charset=utf-8 to match the new payload shape. Other valid encoding values are base64_decode, url_encode, and url_decode. The origin is reached on 127.0.0.1:8080 via the enc.local Host header.

Run

sbproxy serve -f sb.yml

Try it

# Upstream body (what the static action emits internally):
# {"message":"encoded by sbproxy","ok":true}

# Raw response is base64
$ curl -i -H 'Host: enc.local' http://127.0.0.1:8080/
HTTP/1.1 200 OK
content-type: text/plain; charset=utf-8

eyJtZXNzYWdlIjoiZW5jb2RlZCBieSBzYnByb3h5Iiwib2siOnRydWV9

# Pipe through base64 -d to recover the original JSON
$ curl -s -H 'Host: enc.local' http://127.0.0.1:8080/ | base64 -d
{"message":"encoded by sbproxy","ok":true}

# Round-trip through jq after decoding
$ curl -s -H 'Host: enc.local' http://127.0.0.1:8080/ | base64 -d | jq
{
  "message": "encoded by sbproxy",
  "ok": true
}

What this exercises

• encoding transform with encoding: base64_encode
• response_modifiers rewriting Content-Type to match the new body shape
• static action emitting an inline JSON body so no upstream is needed

See also

• docs/features.md - full feature reference
• docs/configuration.md - configuration schema