‘Bitcoin’ (with a capital B) refers to the concept of Bitcoin, i.e. to the technology itself, the protocol, community, or the network. And ‘bitcoin’ (with a lowercase b) refers to bitcoin as a unit of currency.
Let’s take a look at some examples of each:
Examples of Bitcoin with an uppercase B:
“I first heard of Bitcoin in an article in the New York Times back in 2017.”
“In 2021 El Salvador adopted Bitcoin as legal tender.”
“I recently downloaded an iPhone cryptocurency wallet app – and so now thankfully have my own Bitcoin address.”
Examples of bitcoin with a lowercase b:
“My online charity received an entire bitcoin as a donation!”
“Yesterday I bought three bitcoins.”
“I recently exchanged 5 bitcoins for a quarter of a million dollars.”
An example of both ‘Bitcoin’ AND ‘bitcoin’ used within the same sentence:
“The Bitcoin network treats each bitcoin the same, thus establishing a basic level of fungibility.”
Unfortunately however, not all sources agree with the above convention. The official Wikipedia page for Bitcoin states that: “No uniform convention for bitcoin capitalization exists; some sources use Bitcoin, capitalized, to refer to the technology and network and bitcoin, lowercase, for the unit of account. The Wall Street Journal, The Chronicle of Higher Education, and the Oxford English Dictionary advocate the use of lowercase bitcoin in all cases.” So depending on the conventions of the publication you’re reading, the rules may vary! Annoyingly! NOTE: Who better to decide this convention than Satoshi Nakamoto himself (the creator of Bitcoin) however — and within the hundreds of emails he sent whilst developing and explaining Bitcoin (visible at https://nakamotoinstitute.org) he used the convention detailed in this blog post, i.e. capitalized ‘B’ when referring to the network/protocol and lowercase ‘b’ when referring to the currency.
Also: Because in English the convention is to capitalize the first letter of every word that starts a new sentence, it’s possible to see the first letter of ‘bitcoin’ (lowercase) inadvertently capitalized at the beginning of sentences.
Bonus: What do BTC and XBT mean?
‘BTC’ and ‘XBT’ are currency codes (note the more common of these is ‘BTC’) for representing bitcoin, i.e. to be used instead of ‘bitcoin’ (lowercase b).
“Yesterday I bought 7 BTC.”
“Yesterday I bought 7 XBT.”
What About Other Cryptocurrencies and Capitalizations?
It’s impossible to list all of them here of course, but here’s a few of the most popular (and some of the oldest) cryptocurrencies and where each of them stand on this issue of whether to capitalize their first letters or not:
Ethereum (‘Ethereum’ or ‘ethereum’? Capitalize the ‘E’?)
The ‘E’ in ‘Ethereum‘ is always capitalized. It’s never ‘ethereum’. Abbreviated ‘ETH’. As in “I just sent you 9 ETH”.
Litecoin (‘Litecoin’ or ‘litecoin’? Capitalize the ‘L’?)
Litecoin (often dubbed “Silver to Bitcoin’s gold”) follows in the footsteps of Bitcoin by using a capital ‘L’ when refering to Litecoin as a protocol/network and by using a lowercase ‘l’ when refering to litecoin as a unit of currency (although some sources still disagree on this: see the official Litecoin Wikipedia page for examples of the usage we’ve just described). Abbreviated ‘LTC’. As in “I just sent you 9 LTC”.
Dogecoin (‘Dogecoin’ or ‘dogecoin’? Capitalize the ‘D’?)
The ‘D’ in ‘Dogecoin‘ is always capitalized. It’s never ‘dogecoin’. Abbreviated ‘DOGE’. As in “I just sent you 9 DOGE”.
Confused? Hopefully not!