send/docs/faq.md

## How big of a file can I transfer with Send?

There is a 2GB file size limit built in to Send, but this may be changed by the
hoster. Send encrypts and decrypts the files in the browser which is great for
security but will tax your system resources.  In particular you can expect to
see your memory usage go up by at least the size of the file when the transfer
is processing.  You can see [the results of some
testing](https://github.com/mozilla/send/issues/170#issuecomment-314107793). For
the most reliable operation on common computers, it’s probably best to stay
under a few hundred megabytes.

## Why is my browser not supported?

We’re using the [Web Cryptography JavaScript API with the AES-GCM
algorithm](https://www.w3.org/TR/WebCryptoAPI/#aes-gcm) for our encryption.
Many browsers support this standard and should work fine, but some have not
implemented it yet (mobile browsers lag behind on this, in
particular).

## Why does Send require JavaScript?

Send uses JavaScript to:

- Encrypt and decrypt files locally on the client instead of the server.
- Render the user interface.
- Manage translations on the website into [various different languages](https://github.com/timvisee/send#localization).
- Collect data to help us improve Send in accordance with our [Terms & Privacy](https://send.firefox.com/legal).

Since Send is an open source project, you can see all of the cool ways we use JavaScript by [examining our code](https://github.com/timvisee/send/).

## How long are files available for?

Files are available to be downloaded for 24 hours, after which they are removed
from the server.  They are also removed immediately once the download limit is reached.

## Can a file be downloaded more than once?

Yes, once a file is submitted to Send you can select the download limit.


*Disclaimer: Send is an experiment and under active development.  The answers
here may change as we get feedback from you and the project matures.*