CSS Comments

CSS Comments: Documenting and Debugging Stylesheets

CSS comments let you write human-readable notes inside .css files without affecting how browsers style your page. Developers use comments to label major stylesheet sections, explain non-obvious browser hacks, and temporarily disable declarations while debugging layouts.

Single-Line and Multi-Line CSS Comments

Unlike JavaScript or PHP, CSS has only one comment syntax: start with /* and close with */. The same syntax works for brief inline hints and multi-line section banners.

/* ==========================================
   1. Layout Tokens & Base Typography
   ========================================== */
:root {
    --surface-card: #ffffff;
    --ink-primary: #0f172a;
}

.card {
    background-color: var(--surface-card);
    color: var(--ink-primary);
    padding: 20px; /* Matches 8px spacing scale */
    /* border: 1px solid #cbd5e1; Disabled during shadow test */
}

You can toggle comments in VS Code or most editors by highlighting lines and pressing Ctrl+/ (Windows/Linux) or Cmd+/ (macOS).

What Happens in Production Builds

During production builds, tools like PostCSS, Lightning CSS, or Vite strip comments and whitespace automatically to shrink CSS file size. However, if you serve unminified stylesheets directly, remember that visitors can read every comment in DevTools or View Source.

Common Mistakes to Avoid

• Using // single-line comments inside .css files: Standard CSS does not recognize //. A // line corrupts the very next CSS rule until a semicolon or brace resets the parser (though SCSS preprocessors strip // at compile time).
• Nesting /* ... /* ... */ ... */ comments: The first */ closes the entire comment early, leaving the trailing */ as a syntax error that breaks later rules.
• Leaving sensitive internal URLs or TODO notes in public CSS: Keep private endpoints and credentials out of frontend assets.

Frequently Asked Questions

Why does // work in my SCSS file but break in plain CSS?

Sass/SCSS preprocessors explicitly support // silent comments and remove them when compiling down to standard .css, whereas browsers only accept /* ... */ in CSS.

Do CSS comments slow down browser rendering?

Modern CSS parsers skip comments almost instantly, though stripping large comments with a minifier reduces download bytes over mobile networks.