What Makes A Passport Powerful?

Discounting COVID restrictions and border closures, a United States passport will grant you visa-free access to 185 countries as does a British passport. And while that may sound like an impressive number, neither passport qualifies as the most powerful, nor have they since 2015.
​
In fact, according to the Henley Passport Index, the original and most trusted source for global rankings of a passports power, the most powerful passport in the world belongs to Japan. Those who hold a Japanese passport can travel to 191 countries visa-free or with visa-upon arrival access. Japan is followed closely by Singapore, which grants its holders visa-free access to 190 countries. Currently, The United States and The United Kingdom sit at number seven in the rankings for the most powerful passport in the world, along with Switzerland, Norway, and Belgium. Afghanistan ranked last on the list, only granting access to 26 other nations.
So what makes a powerful passport anyway?
 
The Henley Passport Index ranks passports on the basis of a mobility score, or how many countries the passport grants you access to visa-free (and hassle-free). Generally speaking, the higher the mobility score, the stronger the passport.
How powerful is your passport?