Local state

MosaicSync stores its working state in the browser's extension storage. This can include shortcut names and URLs, folders, positions, appearance settings, local artwork caches, and local synchronization metadata. The browser's durable extension-local storage (storage.local) remains the authoritative local copy.

Disposable browser-session caches may use storage.session where the browser provides it. Those caches can be cleared without losing authoritative MosaicSync state.

The optional manual UI-language preference is device-local and stored only in extension-origin localStorage. It is not part of the MosaicSync layout and is not synchronized to other computers.

If you choose or upload custom artwork, MosaicSync stores that image data in its extension-local asset storage. Site-learned favicons and other reconstructable artwork can also be cached locally. Only artwork that is explicitly eligible for browser Sync is handled as described in the Browser account Sync section below; reconstructable and site-learned artwork is not uploaded as Sync artwork.

Profile backup and transfer

When you choose to export a MosaicSync profile, MosaicSync creates a local .mosaicsync file for you to save. The profile is designed as a browser-neutral backup and can include both Spaces, folders, settings, custom artwork, learned favicons, wallpapers, and supported MosaicSync preferences. Profile files are independent of Firefox Sync and Chrome Sync storage quotas.

Exporting a profile does not upload the file to MosaicSync or to a MosaicSync-operated server. When you import a profile, MosaicSync reads the local file you selected, validates its format and integrity, asks for confirmation, and then restores the imported state locally. If browser Sync is already enabled and initialized, the supported imported state can then be published through that browser's own Sync service under the same rules described below.

Browser account Sync

Synchronization is optional. If enabled, MosaicSync writes supported layout records to the browser's extension Sync storage (storage.sync). Firefox transports that data between Firefox installations through Firefox Sync; Chrome transports it between Chrome installations through Chrome Sync. Automatic Sync does not bridge Firefox and Chrome. Cross-browser transfer is available through MosaicSync profile export and import. MosaicSync does not send the synchronized records to a MosaicSync-operated server.

Shortcut URLs and titles, folder names, layout, supported settings, and only eligible compact derivatives of artwork explicitly selected by the user may be included. Reconstructable or site-learned artwork remains outside MosaicSync's binary Sync artwork budget and can remain device-local.

A lightweight repeating extension alarms event checks the browser's already-delivered local storage.sync cache for new commits while Sync is enabled. It does not contact a MosaicSync server and does not itself force Firefox Sync or Chrome Sync network traffic.

Optional bookmarks access

The browser's bookmarks permission is optional. MosaicSync requests it only after the user explicitly opens Bookmarks and chooses to allow access.

When granted, MosaicSync reads the browser bookmark tree through the WebExtension bookmarks API (bookmarks.getTree()) and displays it in a read-only panel. Bookmark folders, titles, and URLs are held in memory only while that panel is open. MosaicSync does not create, rename, move, or delete browser bookmarks, and it does not copy bookmark data into MosaicSync state, storage.local, or storage.sync.

The Bookmarks viewer renders only normal HTTP/HTTPS bookmarks as clickable web links. Bookmarklets and local or file URLs are not exposed as navigable links in this panel.

Optional website access

MosaicSync declares optional host patterns for HTTP and HTTPS websites. They are not required at installation. Website access can be requested from a user gesture for automatic site icons and user-requested web artwork.

There are no content scripts used to profile browsing activity. MosaicSync does not collect page text for profiling or transmission.

Frequently Visited and New Tab shortcut import

If the user enables Frequently Visited or explicitly imports the browser's current New Tab shortcuts, MosaicSync can request the browser's optional topSites permission. MosaicSync uses the browser-provided Top Sites data for those user-enabled features. This data is device-local and is not synchronized as MosaicSync shortcut data unless the user explicitly imports shortcuts into their MosaicSync layout.

Data collection

MosaicSync does not sell data. It contains no developer analytics SDK, tracking pixel, advertising SDK, or telemetry upload endpoint. When synchronization is enabled, the browser's own extension Sync service is the synchronization transport.

MosaicSync is open source and free to use, copy, share, and modify under the Mozilla Public License 2.0.