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Included in:

- user-manual
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When AsciiDoc is converted to embeddable HTML (i.e., the `header_footer` option is `false`), there are only three valid values for the `toc` attribute:

* auto (or unspecified value)
* preamble
* macro

All of the following environments convert AsciiDoc to embeddable HTML:

* the file viewer on GitHub and GitLab
* the AsciiDoc preview in an editor like Atom, Brackets or AsciidocFX
* the Asciidoctor browser extensions

IMPORTANT: The side column placement (left or right) isn't available in this mode.
That's because the embeddable HTML doesn't have the outer framing (or the CSS) necessary to support a side column TOC.