Coffee Bean
en.wikipedia.org

... The two most economically important varieties of coffee plants are the Arabica and the Robusta; approximately 60% of the coffee produced worldwide is Arabica and ~40% is Robusta.[5]

Arabica beans consist of 0.8-1.4% caffeine and Robusta beans consist of 1.7-4.0% caffeine.[6] ...

What that Wiki article does not state is that caffeine is a bitter taste.

Caffeine
https://en.wikipedia.org/wiki/Caffeine

... Caffeine is a bitter, white crystalline purine, ...

So, when you go to Starbucks, you are likely to get a cup of Arabica coffee, because it is more flavorful. But, if you are looking for a caffeine boost, well, maybe dream on ...

On the other hand, if you are a fan of mass-produced commercial ground coffee, you are more likely to be experiencing the higher level of caffeine from Robusta coffee.

Does Light Roast Coffee Really Have More Caffeine Than Dark Roast?
valor.coffee

... Today, we're diving into a common coffee myth: Does light roast coffee really have more caffeine than dark roast? We've seen this conversation be filled with myths and speculation, so today we want to clear this up once and for all!

The Roast Spectrum: Light vs. Dark

Before we dive in here, let's talk about the roasting process. Roasting transforms green coffee beans into the aromatic and complex cups we enjoy daily. Whether you prefer a light roast or a dark roast, each brings unique flavors and characteristics to your cup. ...

Clearing Up the Roast Level Caffeine Myths With Reality

- - - Myth: Light roast coffee has significantly more caffeine than dark roast. Reality: The difference is minimal. Both light and dark roasts contain similar caffeine levels per bean, with any noticeable differences usually stemming from brewing methods or measurement styles.

- - - Myth: Dark roast coffee is stronger and has more caffeine. Reality: Strength refers to flavor intensity, not caffeine content. Dark roasts taste "bolder" but don't necessarily pack more caffeine.

- - - Myth: All coffee beans have the same amount of caffeine. Reality: Caffeine content varies between species. For example, Robusta beans generally contain more caffeine than Arabica beans.

Conclusion

In the end, the caffeine content in light versus dark roast is a matter of how you measure and brew your coffee. Light roasts might yield slightly more caffeine by volume, but the difference is subtle. Your brewing method and personal preferences will ultimately define your coffee experience ....