Apply this guide to your situation
This answer covers “[WPO-006] Remove render-blocking JavaScript without breaking execution order”. Read it with the summary and confirm that the symptom and service match what you are experiencing. Available options can vary by plan and account setup.
- Before changing anything, note what you expected, what happened and roughly when. Check whether the issue affects one page or the whole service.
- Save the full error message and note recent changes. Hide passwords, access codes, personal data and keys before sharing screenshots or logs.
- If a step requires administrator access, restarting services or editing server files, stop if you do not administer that server. Send support the service name, error and checks you have already made.
L3 technical diagnosis
User symptoms
The screen remains blank or incomplete until scripts loaded in the document head finish.
Observed code or message
Lighthouse identifies render-blocking JavaScript requestsLikely root cause
Synchronous scripts in `<head>` pause HTML parsing while they download and execute. Applying `async` indiscriminately can change dependencies and cause errors.
Likely-cause and resolution matrix
Follow a branch only when evidence supports it. A symptom may have more than one cause; do not change layers by guesswork.
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Prerequisites
- Authorised access to the affected site, repository or service metrics.
- A reproducible URL and timestamp; use staging for infrastructure changes.
- A backup or rollback method for configuration and deployments.
Important warnings
- Inspection commands do not authorise production changes. Do not run load tests or global purges without an approved plan.
- Never store private responses in shared caches. Server changes in Anayil Panel depend on the controls available for the service and may require its administrator/provider.
Step-by-step walkthrough
1. Reproduce and narrow the issue
# Find scripts without async/defer; inspect templates and dependencies
rg -n '<script[^>]+src=' src app publicLighthouse identifies render-blocking JavaScript requests
2. Apply the appropriate correction
3. Verify the experience
The improvement is reproducible on the affected route and profile with no new functional errors.
Troubleshooting & Solutions
Lighthouse identifies render-blocking JavaScript requests
Root cause: Synchronous scripts in `<head>` pause HTML parsing while they download and execute. Applying `async` indiscriminately can change dependencies and cause errors.
Resolution: Use `defer` for non-critical external scripts that must preserve order; reserve `async` for independent scripts. Run initialisers when their elements exist and retain fallbacks for essential features.
Rollback and recovery plan
Roll back only the changed directive, dependency or release using the recorded value. If 5xx errors, data exposure or session failures occur, have the operator disable the new rule and retain redacted logs for analysis.
Related runbooks in this category:
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