# Session Data Storage (SDS)
Signicat's standalone Session Data Storage (SDS) is a RESTful web service that lets you upload documents for signing.
Using SDS avoids having to transfer large amounts of data in your web service requests and isolates file transfers from the rest of your business logic.
If you are using our RESTful Sign API, we recommend using the Sign API's built-in Session Data Storage.
If you are an existing customer using DocumentService v3 and PackagingService v4 and have recently migrated to our new platform, the document is uploaded to our Sign API's built-in Session Data Storage (SDS) by using the documents endpoint (opens new window).
Files such as documents for signing orders are uploaded to and downloaded from SDS using plain HTTP, so in order to upload a document, you
HTTP POST it. To download, you
HTTP GET it.
The requests are authenticated using basic authentication, where the username is your service name and the password is the same as in your web service requests. Signicat Support will help you acquire the correct credentials for your integration.
Follow the links in the menu on the left for our SDS user guides and code examples.