Last updated: 2026-07-09
Not every transfer has someone waiting on the other end. Maybe the recipient is asleep, on a flight, or you just want to drop a link in a message and move on with your day. For that, Relayium has a second mode: instead of streaming a file live to another open browser, it encrypts the file where you are, uploads only the ciphertext, and hands you a link you can send whenever — the download happens on the recipient's own schedule.
This guide walks through creating one of these links, the expiry and burn-after-read options, and exactly what the zero-knowledge design means in practice — including the honest limits: creating a link needs the sender to sign in, and links count against a storage quota.
Relayium's realtime mode streams a file directly between two open browser tabs — fast, and nothing is stored anywhere, but both people need to be online together. A stored, expiring link flips that trade-off: your browser does the encryption and uploads the result once, and the recipient can open the link minutes, hours, or days later, on their own time.
Use a stored link when you don't know exactly when the other person will be free, when you're sending the same file to more than one person, or when you just want something you can paste into an email or chat and be done with it.
Creating a link takes a few steps, all in the browser:
Every link needs a lifetime — leaving one live forever isn't the point of a one-off transfer. When you create a link you pick how long it should stay valid, or you can set it to disappear as soon as it's been used once.
Burn-after-read means the link stops working the moment the recipient finishes downloading — useful when the file is sensitive and you want exactly one person, one time, with nothing left dangling afterward. Either way, the recipient sees a live countdown on the download page, so they know how much time (or how many downloads) is left.
Here's what actually happens when you create a link. Your browser generates a random AES-256-GCM key — a different mechanism from Relayium's realtime mode, which negotiates a key between two devices with X25519; a stored link's key is generated locally, with nothing to negotiate. That key encrypts your files and the list of filenames before anything leaves your device, and it's appended to the download link after a `#` — a part of the URL that browsers never send to any server. The server stores the ciphertext it's given, and only the ciphertext; it has no way to decrypt it, because it never receives the key.
That design has real trade-offs worth knowing. The link itself is the only copy of the key, so if you lose it, there's no password reset — the data on the server becomes permanently unreadable. Creating a link requires the sender to be signed in, and every link counts against your account's storage quota until it's deleted or expires. And it's worth being precise about what "zero-knowledge" means here: the ciphertext is genuinely stored on Relayium's server between creation and download — it's just unreadable without the key that never left your browser.
No. Anyone with the full link — including the part after the `#` — can open it and download the files. Only the sender needs to sign in to create the link in the first place.
No. Your browser encrypts the files with a random AES-256-GCM key before anything is uploaded, and that key lives only in the URL fragment, which never reaches the server. The server stores ciphertext it has no way to decrypt — a zero-knowledge design.
You choose when you create the link: 1 hour, 1 day, 3 days, or 7 days, or you can set it to burn after the first complete download instead of a fixed expiry. After that point the link stops working.
Burn-after-read is designed for exactly one download: once the recipient finishes downloading the file, the link stops working for anyone who opens it afterward, so it can't quietly be viewed a second time.
Have a file ready but no one waiting on the other end? Create an expiring link in your browser and send it whenever you're ready.
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