Prepare and verify an offline image workflow
Offline capability depends on the required application and encoder assets already being cached by the browser. Verify the exact device before relying on it away from a network.
Load the production app and encoder first
Visit Ziply while online and allow the page to finish loading. Open the compressor and process a small synthetic image in each output mode you expect to use. This confirms that the current browser can run the local encoder and gives the service worker an opportunity to cache the supplied application assets.
A first visit without a network cannot fetch assets that the device has never received. Private browsing, storage pressure, browser cleanup, and application updates can also remove or replace cached resources.
Run an actual disconnected test
Disconnect the network or use the browser’s offline mode, reload the cached compressor, and process a non-sensitive test pack. Confirm that selection, still-image safety checks, encoding, comparison, individual downloads, and local ZIP creation work as expected.
Test a restart as well as a single tab session. Browser and operating-system storage behavior can differ, so evidence from the exact travel laptop or restricted workstation is more useful than a desktop-only assumption.
Know which features remain online
Stripe Checkout, subscription management, account recovery against the API, and fresh Premium validation require a network. Sponsor advertising and uncached Learn pages also require connectivity. The image bytes themselves do not need those services for local processing.
An unresolved Premium session fails closed if account status cannot be confirmed. Plan important offline work around the features currently available in the tested session, and keep compatible source copies in case a specific output encoder is unavailable.