scalpel@labs: ~/glossary/uncommon-link-schemes.mdx6 sections

Uncommon Link Schemes

Uncommon link schemes are hrefs using a non-standard URI scheme: data: URIs, app-specific protocol handlers (whatsapp:, myapp://), or other non-http URLs. Crawlers can't index them.

extension: Scalpel SEOupdated: 2026-08-14read_time: 1 min
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Why it matters

Crawlers can't follow data URIs or custom protocol links. Any content reachable only via these schemes is invisible to search engines, just like with javascript: links, but for a different reason.

In an audit, these links flag navigation paths that shouldn't be hidden. If a menu or product link uses whatsapp:// instead of a real URL, that's a problem worth fixing.

How it works

A data: URI embeds content inline rather than linking to a file:

<a href="data:text/plain,Hello%20World">Click to see text</a>

App-specific protocols create deep links into native apps:

<!-- WhatsApp share button -->
<a href="whatsapp://send?text=Hello">Share on WhatsApp</a>

<!-- Custom app protocol -->
<a href="myapp://open-page/123">Open in my app</a>

Browsers know how to handle these. Crawlers don't; they need standard web protocols.

What does not matter

Uncommon schemes aren't a ranking factor and won't trigger a penalty. The only issue: is the content behind them reachable via a real, crawlable link elsewhere on the site? If yes, you're fine. If no, you've hidden something important.

Code example

A data: URI embedding content inline:

<!-- This opens a small HTML page in a new tab -->
<a href="data:text/html,<h1>Hello</h1><p>This is embedded content</p>">
  Inline page
</a>

A WhatsApp deep-link that breaks SEO crawlability:

<!-- Crawler cannot follow this -->
<a href="whatsapp://send?text=Check%20this%20out">
  Share on WhatsApp
</a>

<!-- Better: make the link crawlable AND provide the share button -->
<a href="/shareable-page">
  View this page
</a>
<a href="whatsapp://send?text=Check%20this%20out" target="_blank">
  Share on WhatsApp
</a>

How Scalpel shows it

Scalpel flags uncommon-scheme links in the Links panel as a separate category. It reminds you to use standard http or https URLs for any navigation path users or search engines should discover.

Legitimate uses

Data URIs work for embedded favicons or pixels. Don't use them for navigation links; users won't find those in search results. App deep-links (whatsapp://, custom protocols) are fine for installed apps, but ship standard web links too.

Sources