From Longman Dictionary of Contemporary English(I’m) just looking(I’m) just lookingLOOK ATused when you are in a shop, to say that you are only looking at things, but do not intend to buy anything now ‘Can I help you?’ ‘No, thanks. I’m just looking.’ → look kindly on somebody/something at kindly1(3) → look
Examples from the Corpus
(I’m) just looking• "Do you need help with anything?" "No thanks. We're just looking." 