There are several good guides to “digital wills” and one’s “digital legacy” out there, including e.g. handling your Facebook and Google accounts, and I encourage you to both go to those links and research the subject further. A few things seem particularly worth noting, though.
One is that this is yet another reason to use a password manager such as LastPass or 1Password. That in turn becomes an itemized list of your online accounts, and comes with a built-in recovery mechanism which can be used to pass them on to your survivors and/or heirs. LastPass (my password manager of choice) actually has a detailed guide to “preparing a digital will for your passwords,” and third-party guides to using 1Password for this purpose exist as well.
Another is the problem of two-factor authentication. What happens in case of an accident which also destroys your phone or Yubikey? Or if your heirs can’t get past your phone password? Do yourself and them a favor: create 2FA backup codes, and add them to your password-manager emergency-recovery kit.
The more technical you are, the more complex your digital affairs are. For most people we’re just talking about email, social media and photos. But for technical people, and in particular developers, things get more complicated. Do you own domains? Do your heirs even know you own domains, and who the registrar is? Are they technical? If not, by the time they figure that out, the domains may well have expired. Do you have services running on AWS or GCP or Digital Ocean? Do you have private GitHub repos, or public ones with a nontrivial number of stars / forks / issues / wiki pages? Do you administer a Slack workspace?
If you find yourself nodding along to the above, you may want to identify a separate “technical executor” and give them some guidance regarding what you want done with all of the above. Even if they have access, nontechnical people may not really understand that guidance. A little advance work can make it substantially easier for those tasked with taking care of your affairs.
Finally, what about any cryptocurrency you might personally hold? Generally, cryptocurrency wallets come with some sort of recovery seed. Is yours in a safety deposit box somewhere? Do your heirs know it’s in a safety deposit box somewhere? If you want to pass your bitcoins on to them, you’re probably going to have to let them know. (Obviously there is a security trade-off here; depending on how much we’re talking about, you may wish to be more or less cautious about this.)
So, to summarize: Do further research on digital wills, and construct one. Use a password manager, which acts as an itemization of your online accounts and ensure your heirs can access its emergency recovery key. Provide them 2FA backup codes as well, and recovery seeds for your cryptocurrency wallets if any. Identify a technical executor as and if appropriate. Also — and this is pretty key — make sure that a few trusted people know you’ve done all this. Won’t do them much good otherwise.
You may well even have occasion to thank yourself for it, in case of some hardware loss or disaster. Regardless, your heirs will definitely thank you. None of us think that we’ll meet our demise randomly, without warning — but I’m here to tell you, from grim recent experience, it does happen. Be prepared.