Working offline: keep inspecting in the cellar, the crawl space or the loft

Your device holds two kinds of things: the app itself and your work. A service worker takes care of the app. That is a part of the browser that stores a site's files.

When you first open the app, the service worker saves all of its files. After that, the app also opens without a connection. The service worker only stores code, never data.

Your work is kept separately. Every change, photo and setting first goes into a queue and then to the server. For inspections you have open, the app keeps a working copy. Under Instellingen, Gegevens (Settings, Data) you see what is still waiting on your device.

• The app: all files, without data
• The queue: what still has to go to the server
• The working copy: the inspections you have open

The queue and the working copy are stored encrypted in the browser's storage (IndexedDB). Keursnel uses AES-GCM for this, a widely used encryption method.

The key comes from the server, per user. The app can decrypt with it, but the key itself cannot be extracted from the browser.

Your data does not stay on the device longer than necessary.

• Anything sent to the server is removed from the device
• When you log out, everything is removed from the device
• The working copy of an inspection stays for no more than 14 days

As soon as there is a connection, the app sends the queue to the server. Photos go three at a time. In the top bar you see how far the sending has got.

If the connection drops again, the app waits and tries again later. You do not have to do anything yourself.

Work that the server rejects is not silently lost. It stays on your device. You then choose: try again or discard it.

If a colleague's unsent work is on the device, it stays there until that colleague logs in again. And Keursnel saves what you type quickly: a text field saves as soon as you stop typing for one and a half seconds. So you do not have to leave the field first.

A new version of Keursnel only takes effect when you tap Nu bijwerken (update now), or when all the app's windows have been closed.

That way, you choose the moment yourself, for example after the inspection or at the office. The app does not change while you are working on a home.

No. Keursnel is a web app that you open in the browser of your tablet, phone or laptop. You do not download anything from the App Store or the Play Store.

So you do not have to install Keursnel. Working without a connection simply works in the browser.

One caveat: Keursnel has not yet been tested on real tablets and phones, including without a connection. So try it yourself first. Load the sample inspection, put your device in aeroplane mode and inspect a few items.

With a connection, your colleagues' changes come in live. Without a connection, you carry on in your own working copy. As soon as you are connected again, your changes go to the server.

If you have both changed the same field, the last change applies, per field. Input and photos go through the queue in the same way.