Helios Open Reader includes shortcodes for embedding rich content responsively, with automatic dark/light theme detection where supported.

iFrame – [iframe]

[iframe url="https://example.com/embed"]

Embeds any URL in a responsive 16:9 container. Add a title for accessibility (recommended), and optionally set a different ratio:

[iframe url="https://example.com" title="My embedded content"]
[iframe url="https://example.com" title="My embedded content" ratio="4:3"]

Google Slides – [googleslides]

[googleslides url="https://docs.google.com/presentation/d/..." title="Introduction slides"]

Embeds a Google Slides presentation responsively. Paste the "Publish to the web" embed URL. Supports ratio="4:3".

PDF Viewer – [pdf]

[pdf url="https://example.com/document.pdf" title="Course reading"]

Displays a PDF via Google Docs viewer. Default ratio is 16:9. For letter or A4 documents:

[pdf url="https://example.com/document.pdf" title="Course reading" ratio="portrait"]

H5P Interactive Content – [h5p]

Embed via full URL:

[h5p url="https://h5p.org/h5p/embed/123" title="Interactive quiz"]

Or via Content ID (requires H5P Content Embed Source URL to be set in plugin settings):

[h5p id="123" title="Interactive quiz"]

Embedly Cards – [embedly]

[embedly url="https://example.com/article"]

Renders an Embedly card with dark mode support. Useful for embedding links to articles, videos, and other web content with rich previews.