How to diagnose Magento 2 errors

Advice 1

If you see the interface is frozen or looks oddly, but there are no error messages on the screen, then check the browser console for error reports.

Advice 2

If you see just a blank (empty) screen then it could be either a javascript error or a server error.

• To detect a javascript error please follow the Advice 1.
• To detect a server error please follow the Advice 3.

Advice 3

Set the proper error reporting for your PHP interpreter:

• enable display_errors PHP option
• set the error_reporting to a high level (I recommend E_ALL | E_STRICT).

Advice 4

Switch Magento 2 to the developer mode.

Advice 5

See Magento error reports in the var/log folder.
Generally, you can see 2 files there: system.log and exception.log.
system.log usually contains a lot of low-level information and I do not think a generic administrator is able to properly analyse it.
So I recommend to see the exception.log only.

Advice 6

If Magento 2 runs in the production mode (not developer mode) then it does not show the actual error message on the screen, but shows a generic message: There has been an error processing your request and creates a detailed error report in the var/reports folder. You can find the error report file there by its report ID which is shown on the screen.

See also:

• How to diagnose «500 Internal Server Error»
• How to enable the developer mode
• How to see the diagnostic reports in the Google Chrome browser console
• The exceptions are loggged into the var/log/exception.log file
• The non-exceptional messages are loggged into the var/log/system.log file
• The debug messages are logged into the var/log/debug.log file
• How to write a message to a log file?

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