Visible Errors shows notifications right in the page on which the errors occurred, in the top-right corner of the window. They have a “fixed” position, so they aren't affected by scrolling. If you have IFRAMEs in your app, they'll appear inside the frame, when appropriate. They look like this:
You can also customize which domains the extension is active for, so errors only appear on your servers, localhost, etc. Or you can enable errors on all domains, and see how many people have live sites with errors on them, haha. You'd be surprised how many do!
Each error will show for 10 seconds, then disappear. You can also click on errors to dismiss them at any time. They stack along the right side of the page or frame. If your code is generating a flood of errors, only 10 will show at a time. Also, they are de-duped so repeat errors are skipped entirely.
The extension is designed mainly to give you a notification that an error occurred, not provide all the debugging information (stack trace, etc.). Errors are still logged to the console, and that's where you should go if you see an error notification.
To configure which hostnames should show errors, edit the preferences of the extension in your browser of choice:
Go to Safari → Preferences → Extensions → Visible Errors
Go to Window → Extensions → Visible Errors → click "Options".
Enter one or more comma-separated hostname match patterns (* is a wildcard), or leave blank to show errors on every site.
For example, to only show errors for local development and your own website, you could enter:
127.0.0.1, localhost, *.mydomain.com
Visible Errors is always enabled for local files (file://) viewed directly in the browser. However, please note that Safari appears to disable extensions for these types of files (grrrrr), so you'll have to run a local web server to use Visible Errors. Sorry!
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