Yes and no. It depends on a few things.
It’s a well-known fact that deleting things on your computer usually doesn’t completely destroy them. Depending on several factors, it’s possible that files can be undeleted.
So there is definitely some risk in the scenarios you describe.
Deleting webmail traces
Deleting files from your browser or email doesn’t immediately erase the data. Your computer just marks that space as free. To truly wipe it out, you need a tool like Cipher or SDelete. Anything stored at your email provider is out of your control entirely.
Browser cache and history
For almost all web browsers — Chrome, Edge, Firefox, and others — history and cache information are stored in files on your computer. Deleting history or cache means just deleting those files.1 Deleting files on your computer only marks the disk space as unused; it doesn’t overwrite or destroy the data.
In theory, that means it’s possible to recover the information.
Now, I don’t want to make it seem easy. You can’t just flip a switch and recover these files.
For anyone to actually find and make use of them, it would take:
- Luck, in that the space previously occupied by those files hasn’t been overwritten. This luck decreases the longer you continue to use the computer after deleting the files.
- Data recovery software.
- Knowledge of exactly what those files are, what they contain, and how they’re constructed.
But theoretically, it is possible that the information in those files might be recovered.
This is how it works if you access your email via a web browser. Your browser caches things on your hard drive, so the email could be in the cache on your hard drive. There’s no separate email storage on your PC when you’re using webmail.
Email programs
You mentioned only your browser, but I want to point out the email programs installed on your computer — like Outlook (classic), Thunderbird, eM Client, and others — do use separate storage. Most download your email and store it in a database on your computer.
What happens when you delete mail depends on how that particular database software works.
For example, Outlook’s PST format behaves a lot like files on a disk. Emails aren’t actually overwritten; they’re only marked as deleted until you “compact” the PST file or the space is reused by subsequent email. Other email programs use files on a disk more directly. Once again, the files are deleted, but to Windows, that just means they’re marked as deleted, not actually overwritten. Other email programs may work differently.
What I’d call hybrid email programs are even more confusing. These are programs like Outlook (new), as installed on most current Windows 10 and 11 computers. They look and act like an installed email program but are just a wrapper to a browser-based email interface. In these cases, files may be stored locally as well as in browser caches.
Really deleting things
When it comes to truly deleting files, including things like browser caches and history, you need a secure delete or a free-space wipe.
There are two general approaches, both command-line based:
CIPHER /W:C:\SDELETE -c C:
Cipher is included in Windows, and Sdelete (secure delete) is part of the Sysinternals Suite of tools available in the Microsoft Store. Other tools are available online.
Delete a file and wipe the free space, and the file is effectively gone for good. If you’re worried about NSA-level data recovery on a magnetic hard drive, you may have to overwrite the free space more than once; Sdelete in particular has an option to specify multiple overwrite passes.
When it comes to email, on the other hand, there’s no general rule. Outlook’s PST can be compacted to remove all unused space previously occupied by mail that you deleted. Run a free space wiper after compacting to remove fragments of the PST file that may have been left behind.
Again, for other programs, there’s no general answer. It depends on how the program stores its data and what it does when you delete something.
An important caveat for ALL email
Everything we’ve said so far is about what is and is not on your computer.
Remember, though, that email comes to you via your email service provider. When you delete a file at that provider, you have no control over how that email is handled. Even when you empty a “trash” or “recycle” folder online, the email provider could potentially recover those files. For instance, they could recover your email from their own backups.
This type of recovery is rarely, if ever, available to customers like you and me. However, should law enforcement have a reason, it’s possible that the email provider could be forced to recover email you deleted.
Do this
More than anything else, be mindful of what you say in email. Most of us need never worry, as we’re just not that interesting. But if you ever do become interesting, it’s well worth understanding how much of your email conversations could be recovered.
Subscribe to Confident Computing! Less frustration and more confidence, solutions, answers, and tips in your inbox every week.
Podcast audio
Footnotes & References
1: True for cache. It’s possible that the history file is truncated, rewritten, or something similar, but the result is the same: previously stored data could still be accessible in areas of the disk now marked as “unused”.
Just for grins I logged into Outlook.com via a browser and checked my trash folder. (I usually use Thunderbird.) It was empty but there was a note offering to restore 1,349 items that had been “permanently” deleted. That’s way more than I normally receive in any 30-day period. Illustrates that “deleted” doesn’t mean “gone”.
Deleted doesn’t always mean gone. Secure Delete or Wiped means gone in computerese. I’m surprise, Microsoft doesn’t have a Wipe option in the right-click menu. There are third-party apps that add wipe.