What is Compatibility Mode?
When you download your files directly from the web panel Sync uses advanced HTML5 local web browser storage technology to decrypt file data locally. This E2EE feature is fully supported by Chrome (files up to 25GB depending on available local storage space), Firefox and Safari (files up to 500MB in size), Internet Explorer 10+ (files up to 500MB in size) and Microsoft Edge (files up to 500MB in size). This feature is not fully supported by Safari mobile.
If you attempt to download a file that can’t be decrypted by the web browser locally, Sync will download the file in “compatibility mode”.
With compatibility mode, a locally generated share key specific to the file enables data streaming of that file through a Sync-hosted server, to offload local decryption. This is a fully automated process where decrypted data temporarily resides in memory, remains encrypted in transit, and otherwise is not stored by Sync. The benefit of compatibility mode is that that there are no browser-imposed file size limits, video streaming is possible, and virtually all web browsers (eg. Safari) are fully supported.