The difference is `html_safe` allows every HTML tag, including the `<script>` tag, while `sanitize` only allows tags which are considered safe. In this case, we want to allow a `<span>` tag in a translation, and links inside flash messages.
The difference is `html_safe` allows every HTML tag, including the `<script>` tag, while `sanitize` only allows tags which are considered safe. In this case, we want to allow a `<span>` tag in a translation, and links inside flash messages.