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CloudflareDiagnosticsDNS

CDN Serves Old JavaScript After a Successful Deployment

The origin has a new bundle but a CDN still serves an older hash or manifest. Compare asset hashes and response Age headers from CDN and origin.

Quick Answer

Deploy content-hashed filenames and purge the stale HTML manifest selectively. A fresh browser loads the new manifest and all referenced immutable bundles.

What this guide solves: The origin has a new bundle but a CDN still serves an older hash or manifest. Record the context before changing a server, account or data store. A successful unrelated check does not automatically prove that the complete workflow is healthy.

Recognize this failure and establish a baseline

Compare asset hashes and response Age headers from CDN and origin. Record the observed result with its time and environment. If you have multiple sites, service accounts, installations or regions, label them clearly so a working control is not confused with the failing target.

DNS, the CDN edge, TLS termination and the origin are distinct hops. A response that looks correct from one network or cache tier can conceal a rule mismatch or a stale edge copy elsewhere. A precise comparison is usually more informative than clearing caches, restarting every service or changing unrelated permissions. Confirm the reproduction using a harmless sample and preserve the current configuration before editing it.

Three ways to isolate the cause

Diagnostic angle What to inspect Interpret the result
Reproduction and scope Compare asset hashes and response Age headers from CDN and origin. If the control succeeds, the difference between the two paths is evidence; do not change their shared infrastructure first.
Configuration or contract Mutable filenames, service workers and stale HTML references can prevent cache busting. If the setting, identifier or interface differs from its documented contract, fix that discrepancy in the narrowest possible scope.
Runtime and downstream dependencies Inspect browser cache, service-worker update lifecycle and edge TTL settings. If the initial configuration is consistent, use timestamps, error codes and component logs to identify the first failing hop.

First safe fix: change one variable

Recommended correction: Deploy content-hashed filenames and purge the stale HTML manifest selectively. Apply it first in a staging environment or on one limited test object when production traffic, orders or private information could be affected. Write down the previous setting and expected result so a rollback is straightforward.

Why not reset everything? Mutable filenames, service workers and stale HTML references can prevent cache busting. A broad reset can hide the original cause and create additional failures in permissions, orders, certificates or background jobs. If the proposed correction does not change the exact reproduction test, revert it and move to the advanced inspection instead of stacking speculative fixes.

Step-by-Step Troubleshooting

Choose Beginner for reversible checks or Advanced for scoped investigation with sanitized evidence.

Record the failure boundary

The origin has a new bundle but a CDN still serves an older hash or manifest. Capture the precise timestamp, version and one anonymized request, screen or operation. The first objective is to distinguish a consistently failing action from an intermittent side effect; write down what still works.

Perform the smallest comparison

Compare asset hashes and response Age headers from CDN and origin. Keep the account, configuration and data set constant wherever possible. If the comparison requires a staging environment, avoid reproducing it with real payment, customer or production credentials.

Make one reversible correction

Deploy content-hashed filenames and purge the stale HTML manifest selectively. Save or export the setting that will change, note its previous value and alter only this one likely cause. After the adjustment, do not proceed until you have run the same failing operation again.

Prove the outcome

A fresh browser loads the new manifest and all referenced immutable bundles. Repeat the test a second time, including after a safe restart or fresh request when relevant. Verify that a formerly working neighboring feature has not regressed.

Advanced diagnosis: inspect the first failing boundary

Inspect browser cache, service-worker update lifecycle and edge TTL settings. When reading logs, match the same request or transaction across components. A message produced downstream can be secondary to an earlier denial, timeout, incompatible contract or unavailable resource. Use a small known-good request to remove unrelated data from the comparison.

Evidence to keep: Capture the software or protocol version, a masked timestamp, the operation being attempted, the relevant configuration key, and the outcome of the control test. Note both positive and negative findings. If a security rule is involved, preserve the original protection and grant only a narrowly scoped supported exception.

How to verify the repair

Passing result: A fresh browser loads the new manifest and all referenced immutable bundles. Verify the exact operation rather than assuming that an adjacent screen, health endpoint or cached response proves success. Repeat once under normal conditions and check one previously healthy workflow for regressions.

If the result changes only in staging, compare release version, permissions, environment variables and network path with production. If success is intermittent, compare two successive runs and retain the corresponding log evidence before declaring the incident closed.

Solution Checklist

0/12 completed

Safety and rollback

Avoid: Do not globally disable security headers as a cache workaround. Store backups, before-and-after settings and sanitized evidence securely. If the action involves orders, identities, databases or customer information, complete an authorized rollback or request maintenance approval before making another production change.

If it still fails

Return to the first comparison: Compare asset hashes and response Age headers from CDN and origin. Then investigate the remaining owner: Inspect browser cache, service-worker update lifecycle and edge TTL settings. Escalate with a concise timeline and the exact point at which expected behavior differs. Do not send passwords, API keys, recovery codes, complete customer records or private signing material to outside support.

Prevent the next occurrence

Version DNS and edge rules, test both authenticated and anonymous paths, and periodically verify TLS and cache behavior from more than one region. Record the minimum regression test for this exact workflow: A fresh browser loads the new manifest and all referenced immutable bundles. This is more reliable than applying generic maintenance advice each time a dependency changes.

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