Can you speak more about which ones and how that happened? The main one that comes to my mind is the British monarchy (to the extent that they don't really have much power), and my general impression (not a historian) is that that's a bit of a fluke. Looking at the French and American Revolutions, they sort of realized that their necks might stay better attached if they gave some ground. I'm not sure the monarchy being a participant in it's own reform is really applicable.

> The main one that comes to my mind is the British monarchy (to the extent that they don't really have much power)

They don't have much power due to _many, many revolutions_; they may not generally get called that, but the wars leading up to the Magna Carta, and later the English Civil War, were clearly revolutions against the monarchy, and successfully limited its power.

There are more Western European countries with (constitutional) monarchies (The Netherlands, Denmark, Sweden, Norway), that have become less powerful/more ceremonial over the past decades or even centuries.

There are few if any examples of a major absolute monarchy going non-absolute without _some_ sort of revolution (often a kind of limited aristocratic one which may not get _called_ a revolution).

Going from non-absolute to purely ceremonial or non-existent is easier, but generally breaking the power of the monarch in the first place does require some sort of revolution.

That's interesting and sounds like a hole in my knowledge of history. I'm curious, were those monarchies actually dictatorships? The UK still has a monarch, but it's not a dictatorship.

There are basically two kinds of monarchies, absolutist - the monarch has absolute power, so it is actually a hereditary dictatorship - and constitutional monarchy, which is mostly what you see today in the UK, Netherlands, Belgium, Spain etc.

Going further back in the history, some feudal monarchies were actually not absolutist in the sense the king had to manage various factions of landowners, clergy, etc (so-called Estates) or even share power with them. So it all depended on the relative power of the monarch and others in the society.

Then they weren't dictatorships.