Build one layout system with shared structural rules (grid, spacing tokens, component library) and per-locale overrides for the things that genuinely differ by script: font pairing, text-expansion allowance, and date or numeric formatting. Japanese, Simplified Chinese, and Traditional Chinese share a Han-character base but diverge enough in glyph sets, typical copy length, and reader convention that a single hard-coded layout breaks somewhere, while three from-scratch builds waste the structural work that is actually identical.
What Actually Needs to Be Shared Across Japanese, Simplified Chinese, and Traditional Chinese?
The grid, spacing scale, component library, and interaction patterns should be identical across all three locales, because none of the differences between Japanese, Simplified Chinese, and Traditional Chinese are structural. All three are CJK scripts read in horizontal lines on modern web layouts, all three use similar character-density logic, and all three can share breakpoints, button shapes, card components, and navigation patterns without modification. Building three parallel component libraries multiplies maintenance cost for no design benefit: a button that works for one CJK locale works for all three, and a spacing token defined once (base unit, multiplier scale) holds across the set. The place to draw the line is not "one design per language" but "one system, three content variants," which is the same logic covered in more depth for the Japan-only case in Japan Brand Localization: What Foreign Design Teams Get Wrong. Where that post treats Japanese typography and spacing as a standalone problem, the multi-locale version keeps the same structural chassis and swaps only the locale-specific inputs described below.
Where Do Japanese, Simplified Chinese, and Traditional Chinese Actually Diverge?
They diverge in three places that must be decided per locale rather than assumed to transfer: font selection, text-expansion allowance, and date or numeric convention. Each of these is a content-and-asset decision layered on top of the shared structural system, not a reason to rebuild the system itself.
Font pairing is the pitfall most foreign design teams miss first. A typeface licensed and subset for Japanese use does not automatically carry full glyph coverage for Simplified Chinese or Traditional Chinese, and the reverse is equally true: a font built out for Simplified Chinese does not guarantee complete Traditional Chinese coverage, since the character sets overlap but are not identical, and font vendors frequently ship separate subset licenses per script rather than one universal CJK license. Choosing a single "CJK font" without checking the vendor's stated coverage for each script produces missing glyphs or fallback substitution exactly where a client name, an address, or an uncommon surname uses a character outside the licensed subset. This is a licensing and coverage check that has to run once per script, before the font ships to production, not something inferred from how the font renders in one locale's test copy.
Text expansion is the second divergence, and it needs to be measured per script rather than assumed to be uniform across the three. The general principle holds for CJK translation broadly: translated CJK copy tends to run longer than the English source, so a layout built to the English word count risks truncation or awkward wrapping once translated. But the expansion ratio is not necessarily identical between Japanese, Simplified Chinese, and Traditional Chinese, since each language's translation conventions, average character count per concept, and typical sentence structure differ. The only defensible design practice is to check actual translated copy length per locale rather than apply one expansion assumption across all three; a ratio confirmed for Japanese should not be treated as a stand-in for the Chinese variants without its own check.
Date and numeric convention is the third, and it is a formatting decision, not a layout decision: the same date field, in the same position, on the same grid, can render a different string pattern depending on locale convention, and getting this wrong reads as careless rather than merely unfamiliar. This is one of the component-level decisions that belongs in the shared component library with locale-aware formatting logic built in, so the date component itself does not need to be redesigned per locale, only configured per locale.
Key points:
(a) Shared across all three locales: grid, spacing tokens, breakpoints, and the component library itself. (b) Per-locale: font selection with verified Han-character coverage for that specific script, measured text-expansion allowance from actual translated copy, and locale-specific date and numeric formatting rules configured into shared components. (c) The dividing line is structure versus content and asset variant, not language versus language; treat the three CJK locales as one system with three input sets, not three separate design problems.
Where Do Forms Fit Into a Shared CJK Layout System?
Forms are one of the clearest cases of a component that lives in the shared library but carries locale-specific rules inside it, because field labeling, input order, and validation messaging conventions are not identical across English-source design assumptions and CJK user expectations. A single form component, built once, can hold locale-aware label placement, character-count logic for name and address fields, and per-script validation copy, rather than three separate form builds. The detailed pattern for form field placement, label position, and input conventions in the Japanese case is covered in How Should Foreign Companies Design Web Forms for Japanese Users?, and the same "one component, locale-aware configuration" logic extends to the Simplified and Traditional Chinese variants of the same form.
Where Should the Shared-Versus-Per-Locale Rules Live?
They belong in a written brand guideline document, not in individual designers' memory or in scattered Figma comments, because a rule that exists only in one person's head does not survive a team handoff or a new hire. The guideline should state explicitly which decisions are locked at the system level (grid, spacing tokens, component behavior) and which decisions require a per-locale check before shipping (font coverage, expansion allowance, date and numeric format). Structuring this documentation correctly is covered in What Should a Japan-Market Brand Guideline Actually Include?, and the same document structure extends cleanly to a multi-locale CJK guideline: one system section, one per-locale appendix per script.
Aplash's own brand standard requires full parity across English, Japanese, Simplified Chinese, and Traditional Chinese: the same accent color, the same editorial tone, and the same component behavior across all four language variants, with no language treated as a lesser or fallback version of another. That parity requirement is the practical test of whether a shared-system approach is actually working: if any one of the four language variants looks like an afterthought, the system has failed regardless of how clean the code looks. Aplash's design and branding service builds this kind of multi-locale system for foreign companies entering the Japan market, including the font-coverage verification, expansion measurement, and component-level locale configuration described above; more detail is available through Aplash's design and branding service.
Frequently Asked Questions
Can we use the same font for Japanese, Simplified Chinese, and Traditional Chinese?
Only if the font vendor's license explicitly confirms full glyph coverage for each script you intend to use, since coverage for one CJK script does not guarantee coverage for the others. Check the vendor's stated character-set documentation per script before committing to a single typeface across all three locales; if coverage is incomplete for any script, plan a per-script font swap within the same shared layout system rather than forcing one font across all three.
Does Simplified Chinese and Traditional Chinese copy expand from English by the same amount as Japanese?
Not necessarily. The general pattern that translated CJK copy runs longer than English source text holds broadly, but the actual expansion ratio depends on translation conventions specific to each language, so a ratio measured for Japanese should not be assumed to apply unchanged to Simplified or Traditional Chinese. Measure expansion from real translated copy in each locale before finalizing text-container widths.
Do we need three separate design files for a Japanese, Simplified Chinese, and Traditional Chinese website?
No. A single design system with shared grid, spacing tokens, and components can serve all three locales, with per-locale variants applied only where the languages genuinely differ: font selection, text length, and date or numeric formatting. Building three independent design files from scratch duplicates the structural work unnecessarily and makes future updates harder to keep in sync across locales.
Conclusion
A multilingual CJK website does not require three separate design efforts; it requires one system with clearly defined shared rules and a short, explicit list of per-locale checks. The failure mode is not too little design work, it is assuming Japanese, Simplified Chinese, and Traditional Chinese behave identically in the three places they do not: font coverage, text expansion, and formatting convention.
This article is informational only and does not constitute legal, tax, or regulatory advice. Consult a qualified advisor before acting on the content. Last updated: August 2026.