This guide documents link-related safety guarantees and tradeoffs in DeltaHtml.
Scope
DeltaHtml is an HTML renderer for Quill Delta content. It:
- escapes rendered text and attributes via
LazyHTML, - sanitizes link schemes,
- and ignores unsupported embeds (
image,video,formula, etc.).
It is not a full HTML sanitizer for arbitrary HTML input.
Link Sanitization Modes
Default: link_sanitization: :quill
- Matches Quill-compatible behavior.
- Allows
http|https|mailto|tel|sms. - Invalid/malformed links are rendered as
about:blank.
Strict: link_sanitization: :strict
- Allows only
http|https|mailto. - Invalid/malformed links are dropped.
- Recommended for high-trust or compliance-heavy output policies.
Why about:blank Exists
The default fallback preserves link markup while neutralizing dangerous schemes. If your product requires dropping questionable links entirely, use strict mode.
Recommended Deployment Practices
- Prefer
:strictwhere clickable fallback links are not desired. - Keep output rendering in a normal browser sandbox (no privileged webview settings).
- Do not post-process output with unsafe string concatenation.