# `Mailglass.Tracking.Plug`
[🔗](https://github.com/szTheory/mailglass/blob/v2.5.0/lib/mailglass/tracking/plug.ex#L1)

Mountable Plug endpoint for open-pixel + click-redirect URLs.

## Mount

    # In adopter's endpoint or router:
    forward "/track", Mailglass.Tracking.Plug

## Routes

- `GET /o/:token.gif` — 43-byte transparent GIF89a when valid.
  **Failed verify returns HTTP 204** (not 404 — per , no URL enumeration).
- `GET /c/:token` — HTTP 302 redirect to the signed target_url.
  Failed verify returns HTTP 404.

## Security headers

Pixel response:
- `Cache-Control: no-store, private, max-age=0`
- `Pragma: no-cache`
- `X-Robots-Tag: noindex`
- `Content-Type: image/gif`

## Telemetry

Emits `[:mailglass, :tracking, kind, :recorded]` only after a successful
event-ledger append. Returned or raised ledger failures emit
`[:mailglass, :tracking, kind, :failed]` while retaining the GIF/redirect
response. Metadata is `%{delivery_id: binary, tenant_id: binary}` plus a
finite `:failure_class` on failed events — no PII.

# `call`

# `init`

---

*Consult [api-reference.md](api-reference.md) for complete listing*