I agree. Also it might be more convenient when doing get request. Imagine an API generating images like /cat/300x300.jpg the ability to switch to .png is really

I agree. Also it might be more convenient when doing get request. Imagine an API generating images like /cat/300x300.jpg the ability to switch to .png is really handy. Of course you could do /cat/300x300/png and don't use extensions. I think it's up to particular use cases.