A number of differences exist between the Bloomsbury and the Scholastic editions of the Harry Potter books. Most of these differences were made by the US editors to clarify the text for American readers. For example, the UK version uses the term "skip" while the US edition uses the term "dumpster." While some would contend that there is no reason why American readers couldn't work out what a British term means, those kinds of changes do have some logic to them. However, some differences are a bit less easy to explain, such as the change which removed the number of Sirius's Gringotts vault in the US version.

Probably the most infamous change of all is that of the title of book one. Rowling reluctantly went along with the change, which was suggested by Arthur Levine of Scholastic Books. She now regrets her decision to allow the change, she has said, but at the time she felt that she had to go along with the advice of her editors. It never occurred to her that her books would be known the world over and that she would one day wish she could change it back. The change was made and now it's part of Harry Potter history.

In the Lexicon, we originally used SS as our abbreviation for that book. This was a decision I [SVA] made four years ago, before the Lexicon was anything like what it's like now. I only owned the American versions (although since then I have been given a copy of the Bloomsbury edition of book three, for which I am very grateful!) and so I was used to the American version of the title. It never occurred to me that the Lexicon would be known the world over and that I would one day wish I could change it back. The change was made and now it's part of Lexicon history.

Differences between editions of the books
Rowling is actively editing her books to fix errors and to adjust the story to fit the larger saga. As new editions of the books are released, these changes are incorporated into the text. The changes listed below are from a master list of edits circulated by Bloomsbury beginning summer 2004. Many small errors in the text have been fixed with this list. I have not duplicated the entire list here, since many of the fixes are simple spelling or punctuation fixes and of little interest.

book and page	original version	edited version	reason for the change
PS p17/SS p16	"I'll be takin' Sirius his bike back."	"I best get this bike away."	This sentence didn't fit very well with the way the character of Sirius was developed as the series progressed.
PS p56/SS p72	"Dragon liver, seventeen Sickles an ounce, they're mad..."	"Dragon liver, sixteen Sickles an ounce, they're mad..."	Seventeen sickles actually equals one Galleon, so it is unlikely that someone would refer to a price in that way. They would have said "One Galleon."
PS p72/SS p96	Harry noticed a shiny silver badge on his chest with the letter P on it.	Harry noticed a red and gold badge on his chest with the letter P on it.	In book five, Harry sees the badge which Ron and Hermione get when they become Prefects. It is described as red and gold, and Harry realizes that it's exactly the same as the one he saw on Percy several years before. So the text is now changed in book one to make the badges identical.
PS p92/SS p123	"I haven't eaten in nearly four hundred years," said the ghost...	"I haven't eaten in nearly five hundred years," said the ghost...	This change brings the years that Nick has been dead in the first book in line with the fact that the next year he celebrates his 500th Deathday
PS p168/SS p229	Harry, who was lookin up "Dittany" in One Hundred Magical Herbs and Fungi...	Harry, who was lookin up "Dittany" in One Thousand Magical Herbs and Fungi...	The title of the book, according to the booklist from chapter five, is One Thousand... This edit fixes the typo. This error is only found in the British version of the book. The US version is already correct.
PS p193/SS p265	"...yeh get a lot o' funny folk in the Hog's Head--that's the pub down in the village."	"...yeh get a lot o' funny folk in the Hog's Head--that's one of the pubs down in the village."	Since in later books we visit The Three Broomsticks, also a pub in Hogsmeade, this line is changed so that the Hog's Head isn't implied to be the only pub in the village.
PS p205/SS p282	"Well, Harry, you take the place of that bishop, and Hermione, you go next to him instead of that castle."	"Well, Harry, you take the place of that bishop, and Hermione, you go there instead of that castle."	The castle and the bishop are not next to each other on the chess board at the start. The knight stands between them.
PS p205/SS p283	"I take one step forward and she'll take me--that leaves you free to checkmate the king, Harry!"	"I make my move and she'll take me--that leaves you free to checkmate the king, Harry!"	Ron is playing the part of a knight. Those pieces never move one space. They move in a four-space L-shaped pattern.
book and page	original version	edited version	reason for the change
PA3	"So all that remains, " said Fudge, now buttering himself a second crumpet, "is to decide where you're going to spend the last two weeks of your vacation..."	"So all that remains, " said Fudge, now buttering himself a second crumpet, "is to decide where you're going to spend the last three weeks of your vacation..."	There are actually three weeks left in the month of August at this point in the story.
PA4	"I don't want to make him miserable, I want to put him on his guard," roared Mr. Weasley. "You know what Harry and Ron are like, wandering off by themselves -- they've ended up in the Forbidden Forest twice!"	"I don't want to make him miserable, I want to put him on his guard," roared Mr. Weasley. "You know what Harry and Ron are like, wandering off by themselves -- they've even ended up in the Forbidden Forest!"	Harry has been in the Forest twice at this point, but Ron only once.
GF36	"You'll forgive me, Dumbledore, but I've heard of a curse scar acting as an alarm bell before..."	"You'll forgive me, Dumbledore, but I've never heard of a curse scar acting as an alarm bell before..."	This was originally a difference in the text between the UK and US editions. As it turns out, the UK text was in error.

Differences between the British and American versions:

all the books:

Minister for Magic / Minister of Magic
The British form of the phrase uses the work "for." There is no particular reason why this had to be changed for the American versions, since in the US we don't have government ministers at all (ours are called Secretaries). American readers would have been perfectly happy with "Minister for Magic."

Sibyll / Sybill
I have to admit that this one baffles me. I can't find any logical reason whatsoever for this change. In the British versions, Trelawney's name is spelled Sybill. In the US versions, it's Sibyll.

Individual Books:
These pages list the specific changes between the British and American versions of the books. We have tried to include all changes, but every now and then a new one is spotted, and when that happens we do our best to list it here.
Harry Potter and the Philosopher's Stone / Sorcerer's Stone
Harry Potter and the Chamber of Secrets
Harry Potter and the Prisoner of Azkaban
Harry Potter and the Goblet of Fire
Harry Potter and the Order of the Phoenix
Harry Potter and the Half-Blood Prince

Differences between the Books and the Films:
Film is such a different medium than text that changes are not only inevitable, they're necessary for the story to translate. You can think of it as film speaking a different language than text, and in order to make a good film, you have to translate the story into that language. The result is that the first three films are markedly different from the books in many ways. The third film is far more different, actually, but as a result it actually tells the story better than the other two films told theirs, in my opinion. But for fans, these differences can be painful indeed. What many fans consider to be key scenes in the books are sometimes marginalized or completely ignored in the film. On the following pages, we detail some of the most important changes between the film and book versions of the stories.
Harry Potter and the Philosopher's Stone / Sorcerer's Stone
Harry Potter and the Chamber of Secrets
Harry Potter and the Prisoner of Azkaban
Harry Potter and the Goblet of Fire
Harry Potter and the Order of the Phoenix