How to Inspect CSS font-feature-settings JIS04 Proportional Kana and Kanji in Safari Web Inspector

Precision East Asian typography on the web demands strict alignment between Latin numerals, punctuation, and Japanese CJK glyphs. When rendering body copy, editorial narratives, or technical documentation in Japanese, setting OpenType jp04 (JIS2004 standard forms) alongside proportional glyph metrics ensures that character runs achieve harmonious optical rhythm rather than rigid em-square grids. Apple Safari’s Web Inspector provides native font analysis tools that simplify testing and validation of these advanced layout features.

Understanding the Synergy Between jp04 and Proportional Glyph Layouts

The jp04 OpenType feature updates historical character representations to conform with contemporary Japanese publishing standards defined in JIS X 0213:2004. Concurrently, pairing jp04 with pkna (Proportional Kana) and pwid (Proportional Widths) replaces monospaced kana and kanji with proportional character forms tailored for flowing paragraph text. This ensures seamless visual integration between Japanese text runs and embedded Latin scripts.

Declare these OpenType properties using modern high-level CSS properties with fallbacks:

.japanese-proportional-editorial {
  font-family: "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;
  font-variant-east-asian: jis04;
  font-feature-settings: "jp04" 1, "pkna" 1, "pwid" 1;
  text-spacing-trim: space-first;
  line-break: strict;
}

Validating Proportional Glyphs in Safari Web Inspector

To inspect and audit OpenType glyph substitution inside Apple Safari:

1. Launch Safari and navigate to your target page.
2. Right-click on the Japanese text passage and click Inspect Element.
3. Navigate to the Elements tab and select the Font sub-panel located in the right-hand inspection drawer.
4. Expand the Font Features disclosure widget.
5. Verify that both JIS2004 Forms (jp04) and Proportional Widths (pwid) are enabled and highlighted in blue.
6. Use the live text editing input within the Font panel to confirm that glyph runs adopt optical character widths.

Troubleshooting Glyphs and Fallback Rendering

When font features fail to apply as anticipated in Safari, verify the following configuration vectors:

• Subset Stripping: Ensure your web font distribution pipeline has not stripped the pwid feature table during WOFF2 subsetting.
• CSS Shorthand Precedence: Be cautious when using the font: shorthand property on child selectors, as it resets font-variant and font-feature-settings to initial values.
• Glyph Bounds: Ensure parent container widths accommodate tighter optical line lengths without premature wrapping.