A passthrough is a mechanism in AsciiDoc for passing chunks of content directly through to the output. Most passthroughs give you control over which substitutions are applied to the content. AsciiDoc provides both block and inline forms of the passthrough.

The block form of the passthrough is represented either by the ++++ block delimiters or the pass style on a paragraph. The main use of the block form is to pass a chunk of non-AsciiDoc content directly through to the output. For example, you can use the passthrough block to pass raw HTML to the HTML output. However, by doing so, you’re coupling your AsciiDoc content to an output format, thus making it less portable. It’s best either to leave the use of the passthough block up to an extension, or enclose it in a preprocessor conditional.

The inline form of the passthrough comes in more forms and thus has more uses. An inline passthrough is represented by the macro or by pairs of one to three pluses. Only the macro gives you control over the substitutions that are applied. While an inline passthrough can be used to pass raw content like HTML to the output, far more often it’s used as a way to escape content from inline formatting. For example, you can use an inline passthrough to output characters that would otherwise be replaced, such as three sequential periods.