vitejs/vite · error · Error

Unsupported target

Error message

Unsupported target "${e}"

What it means

Thrown by `convertTargets` (the bridge from esbuild-style build targets to Lightning CSS targets) when a target like `esXXXX` has a year not in the supported esMap (currently 2015/2016/2017/2018/2019/2020/2021/2022/2023/2024). css.ts:3628 throws with the offending target string. Only happens when Vite uses Lightning CSS for minification/targeting.

Solutions

1. Use a supported ES year: 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, or 2024.
2. Upgrade Vite to a version whose esMap includes the year you need.
3. Use `'esnext'` (skipped at line 3633) if you do not need a pinned year.
4. Switch `css.transformer` off `'lightningcss'` to bypass convertTargets entirely.
5. Replace `es<year>` with explicit browser targets (chromeXX, firefoxXX, safariXX, edgeXX).

Example fix

// before
export default defineConfig({
  build: { target: 'es2025' }, // not in esMap yet
})

// after
export default defineConfig({
  build: { target: 'es2024' },
})

const SUPPORTED_ES = new Set([2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024])
function assertEsTarget(target: string | string[]) {
  for (const t of Array.isArray(target) ? target : [target]) {
    const m = /^es(6|\d{4})$/.exec(t)
    if (m) {
      const year = m[1] === '6' ? 2015 : Number(m[1])
      if (!SUPPORTED_ES.has(year)) throw new Error(`Unsupported ES target '${t}'; supported years: ${[...SUPPORTED_ES].join(', ')}`)
    }
  }
}

function isSupportedEsTarget(t: string): boolean {
  const m = /^es(6|\d{4})$/.exec(t)
  if (!m) return false
  const year = m[1] === '6' ? 2015 : Number(m[1])
  return new Set([2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024]).has(year)
}

try {
  await build()
} catch (e) {
  if (e instanceof Error && /Unsupported target/.test(e.message)) {
    console.error('build.target contains an unsupported ES year; use a supported year or esnext.')
  }
  throw e
}

When it happens

Trigger: `build.target` or `css.lightningcss.targets` includes `es<year>` (matched by `/es(6|\d{4})/`) where the year is not a key in esMap. E.g. `es2025`, `es2014`, `es2018` is fine but a future/unknown year throws. Reached via the `convertTargets` cache-miss path at line 3628.

Common situations: Setting `build.target: 'es2025'` before the bundled Vite supports it. Typo like `es0215`. Copying a target from a newer Vite version into an older one. Lightning CSS enabled (`css.transformer: 'lightningcss'`) with a target Vite's esMap does not yet know.

Related errors

• Unsupported target
• Failed to load PostCSS config
• Name in package.json is required if option…
• When "build.cssCodeSplit: false" is set…
• config must export or return an object.

AI-assisted analysis of vitejs/vite@b4d66fee14 (2026-08-11). Data as JSON: /api/errors/9b6a50f4c6b3edf8. Report an issue: GitHub.

Appendix: source

Thrown at packages/vite/src/node/plugins/css.ts:3628

const versionRE = /\d/

const convertTargetsCache = new Map<
  string | string[],
  LightningCSSOptions['targets']
>()
export const convertTargets = (
  esbuildTarget: string | string[] | false,
): LightningCSSOptions['targets'] => {
  if (!esbuildTarget) return {}
  const cached = convertTargetsCache.get(esbuildTarget)
  if (cached) return cached
  const targets: LightningCSSOptions['targets'] = {}

  const entriesWithoutES = arraify(esbuildTarget).flatMap((e) => {
    const match = esRE.exec(e)
    if (!match) return e
    const year = match[1] === '6' ? 2015 : Number(match[1])
    if (!esMap[year]) throw new Error(`Unsupported target "${e}"`)
    return esMap[year]
  })

  for (const entry of entriesWithoutES) {
    if (entry === 'esnext') continue
    const index = entry.search(versionRE)
    if (index >= 0) {
      const browser = map[entry.slice(0, index)]
      if (browser === false) continue // No mapping available
      if (browser) {
        const [major, minor = 0] = entry
          .slice(index)
          .split('.')
          .map((v) => parseInt(v, 10))
        if (!isNaN(major) && !isNaN(minor)) {
          const version = (major << 16) | (minor << 8)
          if (!targets[browser] || version < targets[browser]!) {
            targets[browser] = version

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