Abre HTML y explora su estructura como un árbol.
Un árbol de etiquetas te permite ver de un vistazo qué elementos contienen a otros y qué atributos tienen.
Útil cuando el HTML es largo o viene minificado.
The preview frame is sandboxed on purpose. That keeps unknown HTML from running code. To test JavaScript, use your own browser or a dev environment.
Images and stylesheets from other sites may load, depending on your browser. Relative links will not work because there is no base address.
Yes for a rough look. Email clients render HTML differently, so test the final message in the clients you care about.