Site Designer Guide
rsd file-format project backup version-control

File format and project structure

Understanding how Site Designer stores your project helps you back it up, version-control it, and share it with collaborators.

The .rsd file

Site Designer saves projects as .rsd files (the extension stands for Responsive Site Designer). The .rsd format is an XML-based container that stores everything your project needs in a single file:

  • All pages (their HTML structure and content)
  • All CSS styles you’ve created
  • All project settings (framework, breakpoints, metadata)
  • All assets — images, fonts, and other media are embedded as base64-encoded data or referenced internally
  • Page metadata (title, description, slug, custom <head> code)
  • Symbol definitions (reusable components you’ve created)

Because everything is in one file, backing up a project is simply copying the .rsd file. Sharing a project with a collaborator means sending one file — no missing assets, no broken paths.

The .rsdtheme file

CoffeeCup uses a second format, .rsdtheme, for distributing templates and component libraries. An .rsdtheme file contains:

  • A set of pre-built page templates
  • Component library entries (with thumbnails and HTML/CSS)
  • Design tokens and default styles

You can import .rsdtheme files via File → Import Theme. CoffeeCup distributes official themes through the app’s built-in Component Library panel.

Why a single-file format?

Single-file project formats have clear advantages for the typical Site Designer workflow:

  • Easy backup: Copy one file to Dropbox, Time Machine, or an external drive.
  • Easy sharing: Email or Slack one file to a client or teammate.
  • No broken references: Assets travel with the project — no hunting for missing image files.
  • Simpler version control: A single .rsd file in a Git repository means your commits represent complete project snapshots.

The trade-off is file size: embedding images and fonts as base64 makes .rsd files larger than a plain HTML project with separate asset files. For very large projects with many high-resolution images, the file can grow to tens of megabytes.

Assets inside .rsd files

Site Designer handles assets in two ways depending on how they were added:

  • Uploaded assets (images and fonts added through the Resources panel) are embedded as base64 in the .rsd file.
  • Externally linked assets (URLs typed directly into an image src field) are not embedded — they remain external references. These won’t travel with the .rsd file if the external URL becomes unavailable.

Opening .rsd files

.rsd files can only be opened in CoffeeCup Site Designer. They cannot be opened directly in a browser or text editor and used as a website — you must export the project to HTML/CSS first.

To open a .rsd file: use File → Open in Site Designer, or double-click the file in your operating system’s file explorer (macOS Finder or Windows File Explorer).

Backup recommendations

  • Cloud storage: Place your project folder inside Dropbox, iCloud Drive, or Google Drive. All three maintain version history, giving you the ability to roll back to earlier versions of the .rsd file.
  • Git: For developer workflows, commit the .rsd file to a Git repository before major changes. The binary diff isn’t human-readable, but the full snapshots are there for checkout.
  • Manual copies: Before any high-risk operation (switching frameworks, deleting pages, upgrading versions), duplicate the .rsd file with a timestamp in the filename.