The Short Version
Get a link (Safest)
Your files are locked on your device and the only key rides inside the link. FileSeal stores encrypted data it cannot open. You share the link yourself, by WhatsApp, text, or however you like.
Email them (Easiest)
Same encryption, same one-time download, same auto-delete. FileSeal delivers the link to the recipient’s inbox for you, and briefly keeps the key so that link works on its own.
What Both Options Give You
Whichever option you pick, the basics are identical. Your files are encrypted with AES-256 in your browser before they leave your device, so they cross the internet and sit in storage as scrambled data, not readable documents. The download link works exactly once: when your recipient collects the files, the link dies and the files are deleted from storage. If nobody collects them, they expire and are deleted anyway.
That already puts both options well ahead of an email attachment, which is copied onto every mail server it passes through, sits in the recipient’s inbox indefinitely, and can be forwarded without limit. With FileSeal there is one copy, it is encrypted, and it ceases to exist after one download.
So the choice between Get a link and Email them is not a choice between safe and unsafe. It is a choice about one specific thing: who holds the key that unlocks your files.
What Makes a Link Zero-Knowledge
When you choose Get a link, the key that unlocks your files is tucked into the link itself, after the #symbol. That part of a web address is called the fragment, and it has an unusual property: browsers never send it to any server. It exists only on your device and, once you share the link, on your recipient’s.
The result is what security engineers call zero-knowledge: FileSeal stores your encrypted files but has zero knowledge of how to open them. There is no key on our servers, in our database, or in our backups. If someone broke into our storage, they would find scrambled data with nothing to unscramble it. If a court ordered us to hand over your files, we could only hand over the same scrambled data. Not even FileSeal staff can open your files, because the mathematics does not give us a way in.
This is the same design principle behind end-to-end encrypted messaging: the service in the middle carries the data but can never read it. It is the strongest protection FileSeal offers, which is why the button wears the Safest badge.
The honest cost of zero-knowledge
Because nobody but you holds the key, nobody can recover it either. If a zero-knowledge link is lost before the files are collected, the files are gone, and FileSeal support cannot help, no matter how nicely you ask. That is not a flaw; it is the proof the protection is real. If it happens, just send the files again with a fresh link.
Try It Now, No Account Needed
Send a file with a zero-knowledge link in under a minute. AES-256 encrypted, one-time download, auto-delete.
Why the Email Option Exists
If zero-knowledge is the strongest option, why offer anything else? Because the strongest option asks something of you: youhave to deliver the link. Copy it, paste it into WhatsApp or a text, and make sure the whole thing arrives intact. For plenty of people and plenty of situations that is no trouble at all. For others, what they actually want is “put it in their inbox for me”.
That is what Email themdoes. FileSeal sends your recipient a tidy email with a working download link. To make that link work on its own, FileSeal has to keep the key until the files are collected or expire. Your files are still encrypted in your browser before upload, still single-use, still auto-deleted. The difference is that the protection now relies on FileSeal’s security controls holding the key safely, rather than on the key never existing on our side at all.
We think that trade-off is worth offering, and worth being plain about. The picker tells you which option is which before you choose, and this article exists so the label on the button never has to do all the explaining.
Which Should You Choose?
If you can paste a link into a chat you already have with the recipient, choose Get a link. You lose nothing and gain the strongest protection available: a one-time, auto-deleting transfer that not even FileSeal can open.
If your recipient just needs it to land in their inbox with nothing extra to explain, Email them is still a safe, encrypted, one-time transfer, and far better than attaching the file to an email yourself. Choose it knowingly, for the convenience, and you are making a perfectly reasonable call.
Either way, the worst option remains the familiar one: the unencrypted email attachment that never expires, never deletes itself, and gets copied onto servers you will never see. Both FileSeal buttons exist to save you from that.
Related guides
- Email vs Secure Document Sharing. A side-by-side comparison of email attachments and encrypted alternatives.
- Is It Safe to Email Your Passport?. Why identity documents deserve better than an attachment.
- Can Solicitors Use WhatsApp for Client Documents?. Send the link over WhatsApp, never the file.
Send Something Securely Right Now
No account needed. Pick 'Get a link' for zero-knowledge protection, or 'Email them' for convenience. Either way it's encrypted, one-time, and self-deleting.
Written by the FileSeal security and compliance team. We specialise in document security, GDPR compliance, and data protection for UK professionals. Our guides are reviewed by industry practitioners and updated regularly.