grafana/k6 · error

unsupported browser type: %s

Error message

unsupported browser type: %s

What it means

BrowserOptions.Parse rejects any browser type other than the literal string "chromium". k6's browser module is CDP/Chromium-only, so the launcher validates the type option up front and aborts before any process is started. The %s in the message echoes back the offending value.

Source

Thrown at internal/js/modules/k6/browser/common/browser_options.go:70

		Timeout:           DefaultTimeout,
		isRemoteBrowser:   true,
	}
}

// Parse parses browser options from a JS object.
func (bo *BrowserOptions) Parse(
	ctx context.Context, logger *log.Logger, opts map[string]any, envLookup env.LookupFunc,
) error {
	// Parse opts
	bt, ok := opts[optType]
	// Only 'chromium' is supported by now, so return error
	// if type option is not set, or if it's set and its value
	// is different than 'chromium'
	if !ok {
		return errors.New("browser type option must be set")
	}
	if bt != "chromium" {
		return fmt.Errorf("unsupported browser type: %s", bt)
	}

	// Parse env
	envOpts := [...]string{
		env.BrowserArguments,
		env.BrowserEnableDebugging,
		env.BrowserExecutablePath,
		env.BrowserHeadless,
		env.BrowserIgnoreDefaultArgs,
		env.LogCategoryFilter,
		env.BrowserGlobalTimeout,
	}

	for _, e := range envOpts {
		ev, ok := envLookup(e)
		if !ok || ev == "" {
			continue
		}

View on GitHub (pinned to 93accf6570)

Solutions

1. Set the browser type option to exactly "chromium" (lowercase) in the launcher options / script options.
2. If you need Firefox or WebKit, use Playwright directly; k6 only automates Chromium over CDP.
3. Check for typos or capitalized variants such as "Chromium" or "chrome"; only the exact string "chromium" passes.

Example fix

// before
const launcher = launch('firefox');

// after
const launcher = launch('chromium');

// k6 script: fail fast on unsupported browser type before the test runs
const BROWSER_TYPE = 'chromium';
if (BROWSER_TYPE !== 'chromium') {
  throw new Error(`k6 browser module only supports 'chromium', got '${BROWSER_TYPE}'`);
}
export const options = { browser: { type: BROWSER_TYPE } };

function isSupportedBrowserType(v) {
  return typeof v === 'string' && v === 'chromium';
}

try {
  await launch('chromium');
} catch (e) {
  if (/unsupported browser type/.test(String(e))) {
    console.error('Only chromium is supported; fix options.browser.type');
  }
  throw e;
}

When it happens

Trigger: Setting the browser type option in the launcher options map (e.g. NewLauncher(ctx, logger, opts) with opts["type"] = "firefox" or "webkit"), or configuring options.browser.type in a k6 script to anything except "chromium".

Common situations: Porting Playwright test scripts that specify firefox/webkit channels; assuming k6 supports the Playwright browser matrix; typos like "Chromium" (capital C) or "chrome". Note the type option is mandatory: omitting it produces the sibling error "browser type option must be set".

Related errors

• missing required url
• browser not found in registry. make sure to set browser type
• WebSocket endpoint cannot be empty
• k6 couldn't detect google chrome or a chromium-supported bro
• browser type option must be set

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/3a3a7622b94de7c4. Report an issue: GitHub.