Developer tool insights and engineering notes

Why a cleanly formatted XML document can still fail a schema or create unsafe parser behavior, and how to review each boundary separately.

Concrete fixtures for headings, nested lists, fenced code, links, raw HTML, and sanitization when a Markdown formatter changes whitespace.

How standard Base64 and base64url differ, where padding matters, why Unicode needs a byte encoding, and what decoding can never prove.

A practical boundary between parsing, formatting, executable-document validation, variable coercion, and authorization.

Why formatting, sanitization, iframe sandboxing, CSP, URL filtering, and origin isolation solve different HTML-preview risks.