Where the signal fails
Some of the most interesting places for exhibits are poor places for mobile signal. Basements and cellars, thick-walled historic buildings, caves, rural heritage trails, islands and large outdoor sites often have weak or no coverage. Even a modern gallery may have dead spots, or a public wireless network that becomes unreliable when many visitors use it at once.
An exhibit app or web page that assumes constant connectivity will fail visitors in exactly these places. An offline mode is the set of design choices that lets the experience continue, in whole or in part, when the connection drops.
Decide what must work offline
Not everything needs to be available without a connection. A useful way to plan is to sort features into three groups.
- Essential. The core content a visitor came for: text, key images, a map, audio for the main route. This should work with no signal at all.
- Helpful when available. Extra videos, larger images, links to further reading. These can wait for a connection.
- Online only. Live information, sharing, submitting comments or searching a large collection. These simply need a clear message when unavailable.
Be realistic about size. Audio and video are much larger than text and images, so a full offline copy of a rich exhibit can be big. Visitors may be unwilling or unable to download a large package, particularly on a limited data plan, so give them a choice and show the approximate size.
Download before the visit, or on site
There are two broad patterns, and they suit different situations.
Download in advance. The visitor fetches content at home or on the venue’s network before exploring the site. This works well for trails and remote sites. It needs clear prompts, because many people will not think to do it before leaving. Reminders in tickets, on signs at the start of the route, or on the exhibit’s web page can help.
Download at the entrance. A reliable wireless network or a small local device at the start of the visit provides the content. This avoids data costs for visitors but depends on the venue’s own equipment, which then needs care. Planning exhibit networks, as with any connected installation, is part of the work.
In both cases, tell visitors plainly what is happening: what is being downloaded, how big it is, and whether it will work later without a signal.
How the technology fits together
You do not need to use a native installed program to offer offline use. Modern browsers can store pages, images and other files locally so that a web page opens even with no connection. This approach, usually described as storing a local copy of files for later use, lets a web exhibit behave somewhat like an app. The tradeoffs between that and a full installed program are discussed under the choice between a web exhibit and a mobile app.
Whichever route you take, the principle is the same: the device keeps a local copy of the files it needs, and checks for updates when a connection is available.
Handle updates and mismatches carefully
Offline content raises a problem that online sites avoid: the stored copy can fall out of date. If you correct a caption or change a route, visitors with older copies will not see it until they reconnect.
Reasonable habits include:
- Show a version or “last updated” note somewhere in the interface.
- Update quietly when a connection appears, without interrupting someone mid-visit.
- Keep the offline package small enough to refresh without frustration.
- Test what happens if an update is interrupted halfway, so the visitor is never left with a broken mixture of old and new files.
For temporary content such as a changing display, think about which parts must truly be current and which can be treated as fixed.
Design for the moment the connection drops
A good offline experience is mostly about communication. Visitors should always be able to tell whether they are connected, and what the current state means for them. Avoid cryptic errors. A plain statement, such as “This video needs a connection, but the text and images are available,” lets people carry on.
Features that depend on a connection should fail gently. A button that does nothing is worse than one that explains why it is unavailable. Where a visitor’s action cannot be completed, such as submitting a comment, consider holding it and sending it later, while saying clearly that it has not yet been sent. If you collect anything from visitors, remember the usual expectations around visitor privacy, including what is stored on their device.
Keep the interface simple. Offline moments are often moments of confusion, and clear wording, large buttons and consistent navigation help. Following the guidance for cognitive accessibility on simple, predictable navigation applies here as much as anywhere.
Think about the device, too
Local storage is limited and varies by device. Visitors may have a nearly full phone. Avoid storing more than is needed, and make it easy to delete the offline content when the visit is over. Be mindful of battery use as well; a screen in constant use outdoors drains power quickly, and a trail guide that empties a battery by mid-afternoon is no help.
If you provide loan devices, you control the storage and can load everything in advance. That removes many problems but adds others, such as charging, cleaning and replacement. Planning a maintenance plan for those devices belongs in the project from the beginning.
Test where the problems occur
Testing offline behavior at a desk is not enough. Walk the actual route with a phone, switch on airplane mode, and try the whole visit. Test on older devices and with a mixture of strong, weak and absent signal, because the in-between state, where a connection exists but is barely usable, causes more trouble than complete absence. Ask a few unfamiliar visitors to try it and watch where they hesitate.