What causes "creating temporary directory for downloads: %w" in grafana/k6?

Pass an explicit writable path: browser.newContext({ downloadsPath: '/writable/dir' }) on a volume you control

creating temporary directory for downloads: %w

Error message

creating temporary directory for downloads: %w

What it means

When a browser context is created without an explicit downloadsPath, setDownloadsPath (browser_context.go:102) calls os.MkdirTemp(TMPDIR, 'artifacts-*') to create a scratch directory for downloaded files. If the OS refuses — unwritable or missing TMPDIR, ENOSPC, EACCES — context creation fails with 'creating temporary directory for downloads: %w' carrying the syscall error.

Source

Thrown at internal/js/modules/k6/browser/common/browser_context.go:102

	// DownloadsPath is the path where downloads will be stored.
	DownloadsPath string
}

// artifactsDirectory is the prefix for the temporary directory created for downloads.
const artifactsDirectory = "k6browser-artifacts-"

// setDownloadsPath sets the downloads path.
// If the provided path is empty, a temporary directory with
// an artifactsDirectory prefix will be created.
func (b *BrowserContext) setDownloadsPath(path string) error {
	path = strings.TrimSpace(path)
	if path != "" {
		b.DownloadsPath = path
		return nil
	}
	dir, err := os.MkdirTemp(os.TempDir(), artifactsDirectory+"*") //nolint:forbidigo
	if err != nil {
		return fmt.Errorf("creating temporary directory for downloads: %w", err)
	}
	b.DownloadsPath = dir

	return nil
}

// cleanup cleans up the resources associated with the browser context.
func (b *BrowserContext) cleanup() error {
	if err := os.RemoveAll(b.DownloadsPath); err != nil { //nolint:forbidigo
		return fmt.Errorf("removing downloads path: %w", err)
	}
	b.DownloadsPath = ""

	return nil
}

// NewBrowserContext creates a new browser context.
func NewBrowserContext(

View on GitHub (pinned to 93accf6570)

Solutions

Pass an explicit writable path: browser.newContext({ downloadsPath: '/writable/dir' }) on a volume you control
Set TMPDIR to a writable directory for the k6 process
Free disk space or raise emptyDir/ephemeral-storage limits if ENOSPC
With readOnlyRootFilesystems, mount a writable tmpfs/emptyDir at /tmp

Example fix

// before
const ctx = browser.newContext() // auto temp dir in unwritable /tmp

// after
const ctx = browser.newContext({ downloadsPath: '/mnt/vol/downloads' })

Defensive patterns

Strategy: validation

Validate before calling

import { check } from 'k6'
// ensure a writable downloads dir before creating the context
const ctx = browser.newContext({ downloadsPath: '/writable/k6-downloads' })

Prevention

Always pass an explicit downloadsPath on a writable volume
Set TMPDIR to a writable directory in hardened containers
With readOnlyRootFilesystem, mount a writable emptyDir at /tmp

When it happens

Trigger: TMPDIR unset, missing or unwritable; read-only root filesystem in a hardened container; disk full; CI runner with a tiny /tmp; security policy blocking writes under /tmp.

Common situations: Minimal distroless/scratch containers; Kubernetes pods with readOnlyRootFilesystem and no writable emptyDir for /tmp; disk quotas hit in CI.

Related errors

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/a61fe08ee8fc64d9. Report an issue: GitHub.