Is it normal to look older in photos but younger in real life?

I used a "guess my age" website and people thought I was 7 years older than my actual age. So I tried another guess my age website and people thought I was 5 years older than my age.

But in real life, people think I'm 7 years younger than my age nearly all the time. I'm in my twenties and I get IDed by nearly everyone, even had some guy ask me if my ID was fake, etc. When I started my new job, people all thought I was the youngest there when I'm not and when I told them my age, they were shocked and said I looked a hell of a lot younger.

My friends all look their age so they look like older sisters and I've even had people ask if one of my friends was my older sister.

In the photos I uploaded to the guess my age websites, I thought I looked a few years younger than my age..but apparently, based on the guesses, I do look older than my age.

I have no wrinkles or anything so I don't even understand how people could think I look older. In real life, I'm also complimented on my smooth skin, people say I look like I have perfect skin, etc.

So is it normal to look older in photos? Wouldn't it be vice-versa? But it is weird because in other photos of me with my friends on facebook, I definitely look younger as some of the comments are "there's the teenager" and "there's my baby sis" (as a joke).

Am I just shit at taking photos or is it because I'm using my phone to take them? :/ I don't understand this. IIN?