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Specific issues

Here are some resources for specific issues you might encounter

Optimizely app failing to load

If parts of the Optimizely app fail to load, you may need to ask your IT department to change firewall settings. For more information, see Troubleshooting: Variation content doesn't appear in Optimizely Web.

Tools for troubleshooting

Here are some tools to help you identify issues if results aren't showing as you expect.


The logger logs information about your experiments to help you with debugging.

You can customize the log level to the kind of information you want to track and specify where log information is sent. We've also developed default logger implementations for some SDKs.

Error handler

The error handler is called when unknown flag rule keys or event keys are referenced. You can provide your own custom error handler logic to standardize across your production environment.

Event inspector

You can check if events are showing up in the Optimizely app by inspecting events.

Notification listeners

Use notification listeners to trigger callbacks when certain actions are triggered in the SDK.

Reasons in flag decisions

You can access log and error messages in the decision object returned by the Decide call. See the OptimizelyDecision topic in the SDK reference guides for your language for details.