So I did some research on the internet and discovered that they appear to be physically the same size. So if the question is will it fit in the casing, then Yes it can. However, you asked can you use the battery in an iphone 8, which, from what I can tell, the answer to that question is no. First, the connector is completely different. You can see this here: https://d3nevzfk7ii3be.cloudfront.net/ig.... and here: https://d3nevzfk7ii3be.cloudfront.net/ig.... If for some odd reason you found some sort of "adapter", the Watt Hours and the Voltage of each battery are different, which I can imagine the iphone would have a problem with. In conclusion, (Or to save you the reading and research. ;) ) The answer is no.