Why does Windows 10 truncate the user name?

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If you install Windows 10 using a Microsoft account, instead of a local account, it will truncate the username to five letters, and use that as the user directory and a few other things. (you can fix the user directory with this: https://superuser.com/a/955026/310715)

My question, which I can't seem to find an answer to, is why! Why is Microsoft truncating the user name to five characters for linked accounts? To put it another way: why is the truncation taking place and why the (seemingly) arbitrary length?

EDIT: this question was closed as generating primarily opinion based answers. I guess the presumption is that only Microsoft can know the reason why they chose to truncate, and why they chose five characters. But, if they've published their thinking somewhere, or someone has credentialed knowledge, I think there is still an answer out there lurking. Please, if you have information or leads, add comments.

undrline

Posted 2016-11-23T14:39:37.323

Reputation: 449

Question was closed 2017-06-08T02:25:17.530

Not sure if this belongs on "superuser" ... if there's a way to move the question to the appropriate site, I'm all for it. – undrline – 2016-11-23T14:41:59.247

I'm interested, and would like to know more. The whole idea of using a Microsoft registered email address instead of a local account is not a good idea for a lot of reasons, and we must be able to easily switch back and forth, at least. Any other unintended consequences, we should all understand completely so we can mitigate the negative effects. I can see however, why your user folder name should NOT be a long email address. – DaaBoss – 2016-11-23T14:51:44.710

1@DaaBoss, but, rather than truncating at 5 chars, it would make sense to truncate at the commercial at symbol, since that separates the handle from the domain anyway. – undrline – 2016-11-23T15:02:53.007

I'm sure the concept of a single sign in, which is the case for login into a PC that is part of a domain anyway, made sense to Microsoft. User folder names have remained as a cause all types of problems for home users that use multiple PCs. IMO, if your family has trusted users with their own PC, and certainly if you are replacing your PC, using the identical username for all PCs prevents many problems, since all the links and folder names are now identical. – DaaBoss – 2016-11-23T15:54:40.247

1As you implied when you mentioned the previous question that references a similar scenario, the most graceful way to initially setup your Windows 10 profile is to first utilize a local login account, then "convert it" to your Microsoft account. In addition to creating a standard profile folder hierarchy, it also makes a difference when you check online to see which computer names are attached to your Microsoft account (for digital entitlement licenses, etc.). If you use your Microsoft account for initial setup before you rename the computer, that generic computer name is retained online. – Run5k – 2016-11-23T15:58:57.987

Not only Windows 10 but also windows 8. MS live account name will just be truncated without reason. For exampe someuser would become someu – phuclv – 2016-11-23T16:26:45.327

@Run5k - Seeing which PC names are attached to your account by logging into Microsoft is extremely important. Here's why: If you replace your HD, your OEM Windows key is NOT stored in an accessible place anymore, so there is no way for Microsoft to authenticate your PC's new Windows installation. True, even if you have a Dell, Lenovo, HP. By attaching your PC, your PC's fingerprint is recorded by MS, so you can reinstall Windows from a bare DVD with no license key. (Image backup would restore with the key to a new HD.) – DaaBoss – 2016-11-23T17:13:56.007

3I wonder what happens if two usernames shared the same first 5 characters? – Stevoisiak – 2017-06-05T15:08:05.570

I agree with the notion that I'm getting opinion-based answers, but if there is no documentation available or that can be found, I don't know how to re-word the question to stop people from speculation. So, I can't agree with the closure. – undrline – 2017-10-25T15:35:14.503

it seems the problem has been fix, at least from build 17035 – phuclv – 2017-11-18T04:42:11.297

@phuclv no, it hasn't, as I installed latest W10 yesterday. – Alex Zhukovskiy – 2018-08-24T13:28:14.130

1@AlexZhukovskiy I've just installed W10 3 times last weekend and now somehow it truncates my username to 5 letters – phuclv – 2018-08-24T14:31:31.110

It always behave like this and it doesn't seem like MS is going to do something. – Alex Zhukovskiy – 2018-08-24T14:35:19.490

1"5 letters ought to be enough for anybody's name." -Gates – Amit Naidu – 2018-11-04T15:08:51.070

Without a link, I assume that's facetious, @amit_naidu – undrline – 2018-11-05T16:39:25.457

Answers

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More testing is obviously required before this directly answers the question. Without more testing, this answer is incomplete at best.

(YMMV) - Advice for initially setting usernames when installing Windows 10
Anytime you create a new user on a PC, I think you should use a local account first, which sets the user's folder structure name, as in the C:\Users\[localAccount] folder. Then, if you really want to log in with, and attach a Microsoft registered email address to your PC login, it won't change your folder structure.

Since some email addresses would be extremely long, using that for the username which becomes the root folder for the currently logged in user would cause difficulty for programs and users. Often, logs are produced that would then contain that user's email address. These logs often are sent or posted by the user, which would publish that user's email address.

DaaBoss

Posted 2016-11-23T14:39:37.323

Reputation: 1 931

1That's not the problem. I have a real Windows username for the live account like someuser which is completely irrelevant to the live email address, but after I sign in into other computers it'll be truncated to someu – phuclv – 2016-11-23T16:29:14.667

I also want to add that potentially the @ symbol could have multiple meanings aside from it's apparent character, leading to issues with folder names. As far as I remember, folder names cannot contain that particular special character. – Kaizerwolf – 2016-11-23T16:31:33.900

@Kaizerwolf @ is not a forbidden character in filenames – phuclv – 2017-04-19T15:39:34.807

lol, it's funny when I come back to something and want to upvote it again. Like @LưuVĩnhPhúc pointed out, this doesn't answer the problem I posed: why is the truncation taking place and why the arbitrary length? People have argued that the email construct has nothing to do with it. Even if it was a length issue, why davka this length? – undrline – 2017-06-02T16:57:39.727

Clearly, there's more to this than it appears.... I'd like to improve my answer, but I was unaware of many of the issues here, let alone why Microsoft did what they did. My answer was also trying to add something useful to the advice users should use when installing Windows. My testing so far is too anecdotal and limited. However, I will start creating accounts under different scenarios to better understand. Adding to your question, asking for more outside resources to shed some light on the subject might also help. – DaaBoss – 2017-06-05T13:22:20.563

Asked: 2016-11-23T14:39:37.323

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Active: 2018-05-14T17:18:14.933