Firefox Send: Self-Destructing File Sharing Explained
Yes, Firefox Send lets you share files that automatically self-destruct after a set number of downloads or a set amount of time. You upload a file, choose a download limit (1–100) and an expiry period (5 minutes to 7 days), and once either threshold is reached, the file is permanently deleted from Mozilla’s servers. This guide explains exactly how it works, how to use it, and what to know before relying on it.
What Was Firefox Send?
Firefox Send was a free, encrypted file-transfer service launched by Mozilla in 2019. It was designed as a privacy-focused alternative to email attachments or USB drives: you upload a file, get a link, and share that link with anyone. The recipient could download the file before the link expired, and then the file was gone. Mozilla shut down the service in September 2020, citing “maintenance costs� and a need to focus on other products. The code was open-sourced, so self-hosted versions exist, but the original public service is no longer available. If you search for “Firefox Send� today, you’ll find third-party clones or archived versions, not the official Mozilla tool.
How Self-Destruction Worked
When you uploaded a file to Firefox Send, you set two independent limits:
- Download count: 1 to 100 times. After the last allowed download, the file was deleted.
- Time window: 5 minutes, 1 hour, 1 day, or 7 days. The file was deleted after that period, regardless of downloads.
The file was encrypted in your browser using AES-128-GCM before upload. The encryption key was never sent to Mozilla; it was appended to the share link as a fragment (the part after #). This meant the server stored only ciphertext and metadata, and the recipient’s browser decrypted the file locally. Once the file expired, the server removed the ciphertext and the link stopped working.
How to Use It (If You Find a Working Instance)
Because the official service is gone, you can only use Firefox Send through self-hosted or community-run instances. The steps are essentially the same:
- Go to a Firefox Send instance (for example, a self-hosted one you run yourself).
- Drag and drop your file into the upload area, or click to browse.
- Set the download limit (1–100) and the expiry time (5 min to 7 days).
- Optionally enable the password field if you want an extra layer of protection.
- Click “Upload� and wait for the file to be encrypted and uploaded.
- Copy the generated link and send it to your recipient. The link includes the decryption key after the
#symbol.
Important: if you lose the link, you cannot retrieve the file. There is no account system, no recovery, and no way to extend the deadline once set.
Common Problems and Misconceptions
The biggest misconception is that Firefox Send is still an official Mozilla product. It is not. Another frequent misunderstanding is that “self-destruct� means the file is erased from the recipient’s device after they view it—it does not. Once downloaded, the recipient has the file forever unless they delete it themselves. The self-destruct only applies to the copy stored on the server. Also, the download limit counts every attempt, not just successful downloads. If a recipient’s browser prefetches the link or if someone clicks it twice, that can consume a download slot. Finally, the encryption key travels in the URL fragment, so if you share the link via a service that strips fragments (some webmail clients do), the recipient won’t be able to decrypt the file.
Alternatives to Firefox Send
If you need self-destructing file sharing today, several alternatives exist:
- Proton Drive: offers secure file sharing with expiration dates and download limits, though not as granular as Firefox Send.
- Wormhole (by Magic Wormhole): a command-line tool that sends files with end-to-end encryption; the file is deleted from the transit server after transfer, though you can’t set a custom download count.
- FilePizza: peer-to-peer file sharing that uses WebRTC; no server storage at all, so nothing to self-destruct.
- OnionShare: works over Tor, lets you set download limits and expiration times, and is designed for anonymity.
- Self-hosted Firefox Send: if you have a server, you can deploy the open-source code yourself and have full control.
Each has different trade-offs between ease of use, security, and longevity.
Safety and Privacy Considerations
Firefox Send was designed with privacy in mind, but it was not a panacea. The server logs IP addresses and metadata (file size, upload time, expiry) for abuse prevention. The encryption key in the URL means that anyone who sees the link can decrypt the file, so sharing the link securely is crucial. Also, because the service was free, there was no guarantee of uptime or long-term availability—which is exactly what happened. For sensitive files, consider using a tool with additional authentication (like a password) and avoid public instances that might log more than Mozilla did.
Frequently Asked Questions
Is Firefox Send still available?
No, Mozilla shut down the public service in September 2020. The code is open-source, so you can run your own instance, but there is no official hosted version.
Can I set a custom download limit?
Yes, in the original service you could choose between 1 and 100 downloads. The same limits apply to self-hosted versions.
What happens if the recipient doesn’t download before the time expires?
The file is deleted from the server, and the link becomes invalid. There is no way to recover it.
Is Firefox Send end-to-end encrypted?
Yes, the file is encrypted in your browser before upload, and the key is never stored on the server. However, the key is in the URL, so if the link is intercepted, the file can be decrypted.
Can I use Firefox Send for large files?
The original service allowed files up to 2.5 GB if you were logged in with a Firefox Account, and 1 GB without an account. Self-hosted instances may have different limits depending on server configuration.
What is the difference between self-destruct and self-delete?
Self-destruct in Firefox Send means the server deletes its copy after the expiry condition. It does not delete the file from the recipient’s device. Self-delete would imply remote deletion, which is not possible with standard file sharing.
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