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The DevTools panel appears at the bottom of the page. Open the Console tab.
At the top-left of the console, log levels are labeled as Evaluations, Errors, Warnings, and Logs. Make sure only Errors is selected. You can select multiple category filters by command-clicking them.
Once the logs are filtered to show only Errors messages, right-click within the console and select Save Selected. Name and save the file to your preferred location. Alternatively, you can take a screenshot of the messages if you prefer.