Markdown Alerts: Notes, Warnings & Callouts

Quick Answer

Markdown has no standard alert syntax. GitHub introduced blockquote-based alerts in 2023 using the > [!TYPE] format. Obsidian uses a similar but different callout syntax. Other platforms require HTML or emoji workarounds.

> [!NOTE]
> This is a note alert on GitHub.

GitHub Alert Types

GitHub supports five alert types. Each renders as a colored box with an icon:

NOTE

Highlights information that users should take into account.

> [!NOTE]
> This feature requires Node.js 18 or later.

TIP

Optional advice to help users succeed.

> [!TIP]
> Use `--verbose` flag to see detailed output.

IMPORTANT

Key information users need to know.

> [!IMPORTANT]
> Run database migrations before starting the app.

WARNING

Urgent information about potential problems.

> [!WARNING]
> This action cannot be undone.

CAUTION

Advises about risks or negative outcomes.

> [!CAUTION]
> Do not run this in production without testing.

Multi-Line Alerts

Add multiple lines, paragraphs, lists, and code blocks inside an alert by continuing the blockquote:

> [!WARNING]
> Breaking changes in v3.0:
>
> - `config.yml` format changed
> - `--legacy` flag removed
> - Minimum Node.js version is now 18
>
> See the **migration guide** for details.

Obsidian Callouts

Obsidian uses a similar blockquote syntax but with different rules and extra features:

> [!info] Custom Title
> This is an info callout with a custom title.

> [!warning]- Collapsible Warning
> This callout starts collapsed (note the minus sign).

Differences from GitHub

GitLab Alerts

GitLab does not support the GitHub [!TYPE] syntax. Instead, it uses triple-colon fenced blocks (since GitLab 16.7):

:::note
This is a note in GitLab.
:::

:::warning
This is a warning in GitLab.
:::

Supported types: note, tip, warning, caution, important.

Fallback Methods

For platforms that do not support alerts natively, use these workarounds:

Emoji + bold (works everywhere)

> **⚠️ Warning:** This action cannot be undone.

HTML div with background (local apps only)

<div style="padding: 12px 16px; background: #fff8c5; border-left: 4px solid #9a6700; border-radius: 4px;">
<strong>Warning:</strong> This action cannot be undone.
</div>

Note: GitHub and GitLab strip style attributes. This only works in local Markdown apps like MDViewer, Typora, and Obsidian.

Platform Support

When to Use Each Alert Type

Rule of thumb: use at most 2–3 alerts per page. Too many alerts train readers to ignore them.

FAQ

What are Markdown alerts?

Colored callout boxes that highlight important information. GitHub supports five types — NOTE (blue), TIP (green), IMPORTANT (purple), WARNING (yellow), and CAUTION (red) — using blockquote syntax with a [!TYPE] tag. Obsidian calls them callouts and supports additional types and features.

How do I create an alert in GitHub Markdown?

Start a blockquote and add the alert type on the first line: > [!NOTE], > [!TIP], > [!IMPORTANT], > [!WARNING], or > [!CAUTION]. Content goes on the following lines, each prefixed with >.

Which platforms support Markdown alerts?

GitHub supports > [!TYPE] natively. Obsidian uses > [!type] callouts with custom types and folding. GitLab uses triple-colon fenced blocks (:::note). MDViewer for macOS renders GitHub-style alerts. Most other platforms show them as plain blockquotes.

Preview Your Markdown with MDViewer

MDViewer is a native macOS app that renders GitHub-style alerts with proper colors and icons. Open any .md file from Finder to see NOTE, TIP, WARNING, and other alerts exactly as they appear on GitHub. Lite is free; Pro adds editing, Git history, and PDF export.

Requires macOS 13.0 or later. Intel and Apple Silicon.