failed_to_load_clerk_js on your custom domain: the clerk subdomain CNAME is missing

Symptom

On your custom production domain, Clerk components render nothing and the browser console shows failedtoloadclerkjs.

Confirm the cause

1. Open the dashboard's Domains page and compare its required DNS records against your DNS zone. For a production custom domain you need the CNAME record for the clerk subdomain exactly as shown.
2. Check propagation: the record must resolve (not NXDOMAIN). DNS can take up to 24 hours, so a record added an hour ago may simply not be visible yet.
3. Confirm the clerk-js script URL on your clerk subdomain returns 200 in the browser.

Fix

• Add the exact CNAME from the dashboard, wait for propagation, then retest. Do not change code while DNS is still propagating; you will chase a ghost.
• While developing, use the development instance (accounts.dev URLs), which needs no custom DNS at all.

Verify

The script URL returns 200, the console error is gone, and the sign-in component renders on the custom domain.

Verified 2026-09-26: production satellite/custom domains require adding a CNAME record for the clerk subdomain (skippable for development instances); DNS propagation can take up to 24h; the clerk-js script URL on the clerk subdomain should return 200 and the console should no longer show failedtoloadclerkjs.