Apple went from iPhone 8 to iPhone X. Microsoft went from Windows 8 to Windows 10. Both skipped nine, and people have been guessing why ever since.
There are real answers for one of them and only theories for the other. Here is what is actually known, kept separate from what is just repeated online.
Why There Is No iPhone 9
This one is straightforward, and Apple explained it themselves.
The iPhone X launched in 2017, ten years after the original iPhone. The X is the Roman numeral for ten, and Apple named it that to mark the anniversary. It was pronounced “ten”, not “ex”.
Apple had also released the iPhone 8 and 8 Plus at the same event. Calling the flagship the 9 would have made it sound like a small step up. Calling it X made it sound like a new era, which was the point.
So there is no mystery. It was marketing tied to an anniversary.
Why There Is No Windows 9
This one Microsoft never fully explained, which is why the theories multiplied.
What Microsoft said
Officially, the company said Windows 10 represented a big enough jump that the next number did not do it justice. Windows 8 had been unpopular, and putting distance between the new release and that reputation clearly suited them.
The developer theory
The most widely repeated explanation came from developers rather than Microsoft. Older software often checked the operating system name as text, using shortcuts that looked for “Windows 9” to catch both Windows 95 and Windows 98.
If a new operating system were called Windows 9, that old code could mistake it for a system from the 1990s and behave strangely. Skipping to 10 avoided the whole problem.
It is a believable story and it circulated widely, including from people who work in the industry. But Microsoft never confirmed it, so treat it as a strong theory rather than a fact.
What About the Superstition Explanation?
You will often read that the number nine was skipped because it is unlucky in Japan. This is partly grounded in something real, but it is usually overstated.
In Japanese, the number four sounds like the word for death, and nine sounds like a word for suffering. Those associations genuinely exist, and some companies do avoid the number four in certain markets.
But there is no evidence either Apple or Microsoft skipped nine for that reason. And the theory falls apart quickly: iOS 9, macOS 9, Safari 9 and Internet Explorer 9 all existed and sold perfectly well. Plenty of other companies ship products numbered nine without difficulty.
So it is an interesting piece of cultural trivia, not the explanation.
The Short Version
Product |
Reason |
Confirmed? |
|---|---|---|
iPhone 9 |
iPhone X marked the tenth anniversary |
Yes, stated by Apple |
Windows 9 |
Marketing distance from Windows 8 |
Broadly, yes |
Windows 9 |
Old code mistaking it for Windows 95/98 |
No, widely reported theory only |
Either |
Superstition about the number nine |
No evidence |
Will There Be an iPhone 13 or Windows 13?
The iPhone 13 already exists, released in 2021, so that particular superstition clearly did not stop Apple either.
Windows has moved to 11 and beyond, and Microsoft now updates the same version rather than counting upward the way it used to. Whether a 13 ever appears is more about how they choose to version things than about luck.