vitest-dev/vitest · error · Error

Browser " " is not supported by the browser provider " "…

Error message

${name}Browser "${browser}" is not supported by the browser provider "${options.provider.name}". Supported browsers: ${supportedBrowsers.join(', ')}.

What it means

Thrown when the configured browser name (e.g. "firefox") is not in the resolved provider's supportedBrowser list. Each provider declares which browser engines it can drive; asking for one it cannot yields this error with the exact list of accepted names.

Solutions

Read the 'Supported browsers:' list in the error message and set test.browser.instances[].browser (or test.browser.name) to one of those exact strings.
Confirm the provider matches the engine family — playwright supports chromium/firefox/webkit; webdriverio supports a different set.
If you need a browser the provider lacks, switch the provider field to one that supports it.

Example fix

// before
export default defineConfig({ test: { browser: { name: 'safari', provider: 'playwright' } } })
// after
export default defineConfig({ test: { browser: { name: 'webkit', provider: 'playwright' } } })

Defensive patterns

Strategy: validation

Validate before calling

const PLAYWRIGHT_BROWSERS = ['chromium', 'firefox', 'webkit']
function assertBrowserSupported(name, supported = PLAYWRIGHT_BROWSERS) {
  if (!supported.includes(name)) {
    throw new Error(`Browser "${name}" not supported. Use one of: ${supported.join(', ')}.`)
  }
}

Type guard

const SUPPORTED = ['chromium', 'firefox', 'webkit'] as const
function isSupportedBrowser(v): v is typeof SUPPORTED[number] {
  return (SUPPORTED as readonly string[]).includes(v)
}

Prevention

Pin browser names to the provider's documented list in a shared constant.
Treat the error message's 'Supported browsers' list as the source of truth.
Avoid free-text browser names from env vars without validation.

When it happens

Trigger: getBrowserProvider reaches the supportedBrowsers check after options.provider is set, and project.config.browser.name (e.g. 'safari', 'edge') is not included in options.provider.supportedBrowser.

Common situations: Typo in the browser name; using playwright's name with the webdriverio provider or vice-versa; requesting 'safari' (not supported) instead of 'webkit'; case mismatch like 'Chromium' vs 'chromium'.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/35124b6fcf98922a. Report an issue: GitHub.

Appendix: source

Thrown at packages/browser/src/node/utils.ts:84

}

export async function getBrowserProvider(
  options: ResolvedBrowserOptions,
  project: TestProject,
): Promise<BrowserProvider> {
  const browser = project.config.browser.name
  const name = project.name ? `[${project.name}] ` : ''
  if (!browser) {
    throw new Error(
      `${name}Browser name is required. Please, set \`test.browser.instances[].browser\` option manually.`,
    )
  }
  if (options.provider == null) {
    throw new Error(`Browser Mode requires the "provider" to always be specified.`)
  }
  const supportedBrowsers = options.provider.supportedBrowser || []
  if (supportedBrowsers.length && !supportedBrowsers.includes(browser)) {
    throw new Error(
      `${name}Browser "${browser}" is not supported by the browser provider "${
        options.provider.name
      }". Supported browsers: ${supportedBrowsers.join(', ')}.`,
    )
  }
  if (typeof options.provider.providerFactory !== 'function') {
    throw new TypeError(`The "${name}" browser provider does not provide a "providerFactory" function. Received ${typeof options.provider.providerFactory}.`)
  }
  return options.provider.providerFactory(project)
}

export function slash(path: string): string {
  return path.replace(/\\/g, '/').replace(/\/+/g, '/')
}

export function assertBrowserFileAccess(project: TestProject, path: string): void {
  const normalized = slash(path)
  if (

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