# `Mailglass.Tracking.Rewriter`
[🔗](https://github.com/szTheory/mailglass/blob/v1.0.0/lib/mailglass/tracking/rewriter.ex#L1)
Pure HTML transform: open-pixel injection + click link rewriting (TRACK-03).
Called by `Mailglass.Tracking.rewrite_if_enabled/1` AFTER `Mailglass.Renderer.render/1`.
Operates on the CSS-inlined HTML string; returns a rewritten HTML string.
Plaintext body is NEVER modified (D-36 — plaintext readers often go
through text-only proxies; leaving original URLs serves user trust).
## Skip list (D-36)
- `mailto:`, `tel:`, `sms:`, `data:`, `javascript:` schemes
- `#fragment` hrefs (same-page anchors)
- scheme-less relative URLs (e.g. `/signup`)
- `` (attribute stripped from final HTML)
- Any `` inside `` (prefetch, canonical)
- Any href equal to the List-Unsubscribe URL (v0.5 hook reserved)
## Pixel injection (D-37)
Markup: `
`
Position: LAST child of ``. Missing `` → appended at root.
`alt=""` prevents screen-reader announcement.
# `rewrite`
*since 0.1.0*
```elixir
@spec rewrite(html :: String.t(), opts :: keyword()) :: String.t()
```
Rewrites an HTML string applying open-pixel injection and/or click link rewriting
based on the provided flags.
## Options
- `:flags` — `%{opens: boolean, clicks: boolean}` (required)
- `:delivery_id` — delivery UUID for token encoding (required)
- `:tenant_id` — tenant scope for token encoding (required)
- `:endpoint` — Phoenix.Token endpoint or secret binary (optional, falls back to config)
---
*Consult [api-reference.md](api-reference.md) for complete listing*