Markdown Highlights: Equal Signs Syntax Guide

==Highlighted text phrase==
**==Bold and highlighted text==**

Text highlighting simulates the experience of marking a physical book or printed manuscript with a highlighter pen.

In knowledge synthesis, academic research, meeting debriefs, and literature review, highlights allow you to skim documents rapidly, pulling out pivotal conclusions, core metrics, and critical action items without altering the original prose.

Supported natively by Obsidian, CriticMarkup, and Oyma, double equal signs (==) provide clean inline highlighting with zero HTML tag overhead.

Basic highlight syntax

To highlight a word or phrase, wrap the text with double equal signs (==):

Oyma records both sides of a meeting with ==no bot joining the call==.
Full-text search executes locally with ==sub-50ms query latency==.

In the rendered view:

• The bounding == characters are hidden.
• The text is wrapped in the semantic HTML <mark> element.
• A subtle, high-legibility background tint is applied behind the characters.

Delimiter whitespace rules

Like bold and italics, highlight delimiters must touch the target text directly without intervening spaces:

<!-- INCORRECT: Spacing breaks the highlight -->
== this text will not highlight ==

<!-- CORRECT: Delimiters touch text directly -->
==this text highlights cleanly==

Combining highlights with other Markdown formatting

Highlights nest seamlessly with other typographic styles:

Bold highlights

**==Critical architectural invariant: All files remain plain text on disk.==**

Italic highlights

*==Key takeaway from customer discovery interview==*

Inline code within highlights

==Verify the local SQLite FTS5 index using `pnpm verify`==

HTML fallback for strict CommonMark parsers

If you need to share a Markdown file in an environment that strictly adheres to vanilla CommonMark (such as a GitHub repository README where == is not parsed), you can use the standard HTML <mark> tag:

This sentence contains <mark>highlighted text</mark> using standard HTML.

Because CommonMark preserves valid HTML tags, <mark> is universally supported across all browsers and Markdown previewers.

Highlighting workflows in Oyma

In Oyma on macOS:

• Select any word or phrase and press the customizable keyboard shortcut (or type ==) to wrap the selection immediately in highlight markers.
• In live-preview mode, highlights employ dynamic design tokens that adjust contrast ratios automatically when switching between macOS Light Mode and Dark Mode. This avoids eye fatigue while retaining crisp typographic hierarchy.
• When your cursor moves into a highlighted phrase, the == delimiters reveal themselves instantaneously for precise character edits; once your cursor exits, the markers collapse back into clean visual highlighter ink.
• Files remain 100% standard plain text on your Mac disk, accessible by any text editor or CLI utility.

AST node representation and compilation

Under the hood, extended markdown engines like remark (with remark-mark) parse ==highlighted text== into an abstract syntax tree (AST) node typed as mark or highlight:

{
  "type": "mark",
  "children": [
    {
      "type": "text",
      "value": "Critical architectural invariant"
    }
  ]
}

During HTML generation, this AST node serializes directly to semantic <mark>Critical architectural invariant</mark>. When exporting to PDF or printing, your print stylesheet can style this tag with subtle background tints (background-color: var(--color-mark-bg)) without obscuring the underlying glyphs.

Search indexing and highlighted text extraction

Because highlight tokens (==) are stored directly in raw plain text, terminal search tools like grep, ripgrep, and desktop utilities like Spotlight index the text without obstruction:

# Search for highlighted phrases across your entire vault
rg '==([^=]+)==' ~/Documents/Notes

In Oyma, the embedded SQLite FTS5 search engine tokenizes words within == delimiters as standard indexable terms. You can find key passages instantly by searching for exact phrases, even if you do not remember whether you highlighted them. This provides bidirectional utility: visual scanning during review, and fast full-text recall during research.

Frequently asked questions

What is the syntax for highlighting text in Markdown?

Enclose the target words between double equal signs: `==highlighted text==`. This compiles to the HTML `` element, applying a colored background highlight.

Does standard CommonMark support the double equal sign highlight syntax?

Standard CommonMark does not define highlights; highlighting is an extension supported in Obsidian, Oyma, CriticMarkup, and various Markdown previewers. In environments lacking support, standard HTML `text` can be used.

Can highlights be combined with bold, italic, or strikethrough formatting?

Yes. You can nest delimiters: `**==Bold and highlighted==**` or `~~==Struck through and highlighted==~~`. Delimiters must be balanced symmetrically.

How does Oyma display highlights in the live-preview editor?

Oyma immediately applies an elegant, high-contrast background tint to highlighted text while concealing the bounding `==` markers when your cursor moves away.