There are several different ways to work out the size of an image which appears on a website.

I'm using a Mac with Firefox browser, so I'll show you the instructions I follow using the Control key and the mouse. I think you also use the Control key on a Windows pc ... but not 100% sure as I haven't used one for a while :-)

Here's the quick video I've created to show you how I do it:

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I hope this makes sense and is easy for you to follow along. If you have any questions, please do let me know :D