We bought a rescue Silky Terrier, who came microchipped - and she was 5 years old. The chip didn't work when scanned - so I gave up on that for both of my dogs. Since we never let them out of our sight while out, and we have a fenced backyard (with huge blocks at the bottom of the fencing to keep them in and other critters out), we're safe. They come in & out of their dog door as they like, and are very safe & happy in their home.