How to Inspect CSS font-feature-settings JIS04 Proportional Numbers 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 pnum (Proportional Figures) ensures that numeric characters occupy optical character widths rather than rigid tabular columns. 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 Numbers (pnum)

The jp04 OpenType feature updates historical character representations to conform with contemporary Japanese publishing standards defined in JIS X 0213:2004. Concurrently, the pnum tag replaces fixed-width tabular numerals with proportional figures tailored for flowing paragraph text. This ensures seamless visual integration between Japanese kanji and embedded Arabic numerals.

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

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

Validating Proportional Figures 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 containing numbers 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 Figures (pnum) are enabled and highlighted in blue.
6. Use the live text editing input within the Font panel to confirm that numeric inputs 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 pnum 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.
• Tabular Font Overrides: Verify that parent container styles do not apply font-variant-numeric: tabular-nums.