Internationalization ​

Both rendering engines draw text with whatever fonts the host OS / container provides — the default skia engine uses the system font stack directly, and the browser engine uses Chromium's usual font stack. The Docker image bundles Noto Sans CJK (used by both engines), which covers Japanese, Chinese, and Korean without tofu.

Japanese labels ​

PreviewJSONCLIHTTP

Why it works ​

• In Docker: the Dockerfile installs fonts-noto-cjk. Both the skia and browser engines pick it up automatically as the fallback for CJK glyphs.
• On your host (without Docker): whatever your OS uses. On macOS and recent Windows, CJK just works. On fresh Linux minimal installs, you may need to apt install fonts-noto-cjk or similar.

Verifying a non-default locale ​

Quickest smoke test:

# JA
echo '{"type":"bar","data":{"labels":["東京"],"datasets":[{"data":[1]}]}}' \
  | chartjs2img render -o /tmp/ja.png

# ZH
echo '{"type":"bar","data":{"labels":["北京","上海"],"datasets":[{"data":[1,2]}]}}' \
  | chartjs2img render -o /tmp/zh.png

# KO
echo '{"type":"bar","data":{"labels":["서울","부산"],"datasets":[{"data":[1,2]}]}}' \
  | chartjs2img render -o /tmp/ko.png

If any of those render as boxes, check font install on the host (or use the Docker image).

Right-to-left scripts ​

RTL (Arabic, Hebrew) also render correctly — Chart.js plus the underlying engine (Skia or Chromium) handle the text layout natively. Punctuation and bidi isolates behave as expected. We don't ship an RTL-specific font pack; the glyph coverage of Noto Sans gets you there on most systems.

Forcing a specific font ​

Set the font family in one of three ways (Chart.js options.font.family cascades down to every text element):

• CLI: --font-family "<name>"
• HTTP: "fontFamily": "<name>" in the request body
• Library: the fontFamily render option

Via the CLI and HTTP the name must be a font already installed on the host (the default skia engine reads the system font stack; the browser engine reads Chromium's).

Bring your own font (library, no system install) ​

From the TypeScript library you can register a font package — e.g. an @fontsource/* — and render with it on the skia engine without any system font installed. This is the easiest way to guarantee CJK / multi-language output in a minimal container:

import { renderChart, registerFonts } from 'chartjs2img'
import { createRequire } from 'node:module'
const require = createRequire(import.meta.url)

// bun add @fontsource/noto-sans-jp
await registerFonts({
  'Noto Sans JP': [
    require.resolve('@fontsource/noto-sans-jp/files/noto-sans-jp-japanese-400-normal.woff2'),
  ],
})
await renderChart({ chart, fontFamily: 'Noto Sans JP' })

Register several script subsets under one family name for combined coverage. See Library API → Custom fonts for details. (Registration is library-only; the CLI and HTTP fontFamily just select an already-installed font.)