As suggested by the others, I would use a work-related mail.

However, I would suggest thinking ahead and don't use your personal work mail but one which is tied to your team or is set up especially for using to register at work-related websites. Something like developerteam@compayname.com.

This has the advantage that, if you leave the company its easy for someone to pick and use your accounts without the risk of exposing your emails.

It all depends.

For something like StackOverflow I use my personal account as that is something that follows me from job to job.

If I'm registering something particular to my current position I used my work email.

As a general rule, don't co-mingle work and personal accounts

Use work accounts for work and setup separate personal accounts for personal use. Many many things can go wrong if you use personal accounts for work:

1. 
   It can lead to "whose account is it?" disputes: you own the account but the company relies on it and it may contain company data; whose is it now? Everyone's and no-one's. If you leave the company it's possible that the company (their lawyers) may demand that you provide them access to your account (I've read about this more than once on Stack Exchange). Are you okay with that? It's best to avoid this awkward and potentially legally complicated situation if you can.


2. 
   It can lead to data spills: are you prepared to lose years worth of personal emails because a service unexpectedly leaked proprietary company data to your personal email account (e.g. an automated Jira email contains a comment with legally-protected proprietary information)? What if a spill violates privacy or other laws (note: if you in any way work in healthcare or with the government or a government contractor this is especially important).


3. 
   It can lead to complicated hand-offs: are you going to give your personal password to the company when you leave the project or company? Probably not, so they will have some work to do if/when you leave, and in the meantime it will cause unnecessary hard feelings.


4. 
   It can put the company at risk if your account is hacked: suppose your personal account is hacked and used to try to exfiltrate company data (more common than you think), insert malware on the company network, or otherwise gain unauthorized access. Now it's "your fault" because it's your personal account. Not a fun situation to be in, and on top of it you may find yourself with a leak of confidential data into your personal account that has to be cleaned up (and possibly by your company, meaning turning over your credentials). There could be legal repercussions for the company and for yourself if the spill violates any laws.

In summary, just don't do it.

The sharp line is whether company assets and data will be involved

... And company assets and data should not be involved if the company hasn't authorized use of the site for those assets or data.

Another way to think of this is, "when you leave, will the signup/login be part of the hand-off?" Or should your replacement really be getting their own account?

As an example, StackExchange. If you are using the site for your professional edification, then the edification is for you the person since the lessons will remain in your brain.

If you are only viewing or downloading assets that are free but behind a signup-wall, then signups are disposable and it's a tossup either way. Consider the nature of the account and its customizations, and revisit the question of whether, if you were replacing another person in a role, you would expect the account to be handed off to you.

Other than any of that, I would tend to let accounts be personal.

Don't let the web site decide. For instance if you set up a PayPal account for your company to accept Visa-MC, PayPal will keenly ask a bunch of questions about YOU, and will even demand your personal SSN. That does not make it your account obviously. (It may make it a bad choice of vendor, but PayPal does this because of Know-Your-Customer laws).

If its work related, use your work email address.

As stated, you have work tasks that require you to access information on these websites. I cant imagine a company viewing this as personal.

I've faced this issue before and in my opinion it would be ok (or even best) to use your personal email for this.

Multiple reasons for this:

• You might need these tools, info, ... for personal use or for other
  projects where you might not have access to you work email.


• You avoid any spam reaching your professional email.


• You prevent the companies offering these tools from gathering data
  on/about your company, which may push them to reach out to it etc.


• As there is no requirement from your company to use these, there
  is also none for you to connect your professional mail to them.

Of course if you're not allowed to access any personal email or such then the above would not really matter

I have a dedicated GMail-address for this name-work@gmail.com. I don't use this address for any personal stuff, just work related accounts, mailing lists and similar - that is, if my employer seizes my computer and gets access to this account they won't find anything interesting.

However, this solution it is pretty useful because on your next work you might need an account at Oracle again and if you have used your @work-address the first time you signed up you probably need to re-register a new account.

While all the other answers are clear cut, I can see why you’d hesitate. Take SE itself, for instance, the line between work and personal is blurred. What might start off as "work only" might transition to personal, too and vice versa. Why not use your "personal" rep to start a bounty to get a "work" question answered quickly?

To account for that, I’d add that many sites have provision to change your registered email address (or merge accounts) should you (e.g.) leave your current company but wish to retain your membership. It’s in their best interests to keep members, too.

But you should remember to do it while you still have access to both accounts, and remember to delete anything that isn’t explicitly your IP. While I don’t think anyone will come after you for a SE question, github and dockerhub are just about perfect places for unwitting IP leakage. It might be simpler just to start again.

I suggest using your personal E-mail account because you may want to use the same site for personal reasons later on.

Generally I use the company E-mail account only when the company specifically requires me to do so.

My company doesn't require me to use these websites, I just want to register at them because some specific task asks for it, or just because I want to.

As stated in your question, this is clearly not the case. Using your personal account is more appropriate.

It depends on you company's policy and what websites / tools are we talking about.

Personally I prefer to use a personal account for management tools, git repositories and other dev tools and websites I use unless I get specific instructions not to do so or if I am sure I will not use the account in case I leave.

I will however not mix my personal account with my work email account, or a company PayPal account with my own.
If we're talking about StackExchange (just as an example), I'd rather use my own account.

Are you supposed to transfer the account to your company when you left?

If yes, you should use a transferable work email.

If it's clear you should keep the account, you should use your personal email. Companies could have specific rules against this in every case. But a github account could have contributed to both company and personal repositories, and there is the flight mileage thing. I'll not assume anything the usual practice, and recommend you not, but clearly some companies are not against this. It may be even impractical to create and use company accounts on some shopping sites, unless you have the highest authority.

If nobody cares, it's likely the account will be permanently inactive. But if you don't think it belongs to you anymore anyway, better assume it belongs to your company. But don't think about that too much.

To be clear, I consider edu emails ambiguously personal or not, and will not discuss it in this answer.