Introduction

An app migration can move the site successfully while incoming webhooks still post to the old domain. The main website may already load from the new platform and manual API tests may pass, but third-party services keep delivering event callbacks to the legacy endpoint because their saved webhook URL was never updated.

Treat this as an external-callback target problem instead of a general application outage. Start by checking the exact webhook destination configured in the sending platform, because many post-migration failures come from vendor-side callback URLs that remain pinned to the previous domain long after the site itself moves.

Symptoms

  • Webhooks still post to the old domain after migration
  • Manual requests to the new endpoint work, but third-party event delivery still fails
  • Provider delivery logs show attempts against the previous hostname or URL path
  • Some integrations work after cutover while one vendor or service still hits the legacy domain
  • Events appear delayed, duplicated, or missing because callbacks go to the wrong destination
  • The issue started after domain migration, app cutover, or API endpoint replacement

Common Causes

  • The webhook sender still stores the old callback URL
  • The new app moved to a different hostname, path, or routing pattern than the previous environment
  • One vendor integration was excluded from the migration checklist and never updated
  • Legacy redirects, proxies, or expired certificates on the old domain hide the real callback failure
  • Teams validated interactive app traffic but not inbound webhook destinations from third-party systems
  • More than one webhook endpoint exists, and only part of the integration was updated

Step-by-Step Fix

  1. Identify the exact webhook sender and event flow that still fails, because you need the real external delivery path before changing application routing.
  2. Check the saved callback URL in the sending platform and record the full hostname and path it uses, because webhook problems after migration usually start with one vendor-side endpoint that still points to the previous domain.
  3. Compare that configured URL with the intended post-migration endpoint, because the new app may use a different hostname, path, or versioned route than the old system.
  4. Review delivery logs or recent failed webhook attempts from the sender, because they usually confirm whether requests still target the retired domain or another stale endpoint.
  5. Update the webhook URL at the actual source of delivery rather than relying on redirects, because callback traffic should point directly at the supported live endpoint after migration.
  6. Retest with a new event or provider resend after the change, because one corrected setting is not proven until the external service actually delivers to the new domain.
  7. Verify the new endpoint processes the webhook successfully and no longer depends on the old hostname, because successful network delivery alone does not confirm application-level recovery.
  8. Review related integrations from the same vendor or workflow if multiple webhook endpoints exist, because migrations often miss one callback while another appears fixed.
  9. Document every third-party callback URL updated during the cutover, because webhook destinations are easy to overlook in future app migrations.