Seamless Experiences Anywhere: The Rise of Offline Accessibility in Web Apps.

Written by Tomás Orozco.

As internet connectivity grows and becomes increasingly relevant for global users, there is a growing focus to implement applications that function efficiently in rural areas, or areas with inconsistent internet connections. When building apps, relying solely on connectivity can lead to frustration for users with poor or no connectivity at all. This is where this idea comes into play.

A trend followed by front-end developers is offline accessibility in web applications. Offline accessibility means accessing valuable content from the browser even when the internet is not connected. Offline and progressive web experiences are web applications that can work, even when the network is slow, unreliable, or unavailable. Examples of some popular offline apps are Spotify, Kindle and Google Maps. Some of the most modern technologies and techniques that enable offline accessibility are app caching, service workers, PWAs, and local data sync. So, what can each one do?

1. App Caching: Is a way to store data that is frequently used or expensive to generate in a temporary storing location, usually called cache, for a faster retrieval. The cache can be located on the client side, such as the browser or a proxy server, or on the server side, such as the database or a web server. The main benefits of caching is to reduce load times, improve performance and user experience, by instead of using the network calls repeatedly to obtain information, obtain first the cache data.
2. Service workers: Are JavaScript scripts that run independently of the main application thread. They can be used to intercept network requests, caching assets and managing updates in the application. The most important part is that they provide a layer of abstraction between the application and the network, allowing efficient data fetching and storing during offline usage.
3. PWAs (or Progressive Web Apps): Are a type of application built using web technologies, but provides a user experience like a platform-specific application. Since they are a web application, they can be accessed from multiple platforms and devices, and since they are platform-specific, they can be installed on the device, can operate offline in the background, and can integrate with the device and other installed apps. Most popular frontend frameworks, such as Angular and React, allow for an easy creation and configuration of PWAs.
4. Local Data Sync: Is a process of keeping the data stored or displayed on different devices in sync with each other, which may involve transferring data, solving and handling errors. This allows users to access and update data from any device, even when offline or in a slow connection. It can reduce load times by caching data locally and sending only the changes of the data to the network when needed.

Pitfalls and Common Mistakes

When building these kinds of apps, there are some considerations that the developers must take into account. Developers should not assume that they can have unlimited storage space for caching data. It is recommended to implement checks and balances to handle storage limitations gracefully. Another common mistake is to not fully test the offline capabilities of the application, they might only concentrate on testing only online functionality. To address this, they should test in a variety of network conditions, and consider implementing end-to-end tests that simulate offline scenarios. It is also common to leave the UI static, without any feedback to the user, when utilizing the offline mode of the application. Developers should add a message, or inform the user when they are in offline mode, that their actions will sync when the connectivity is restored. Lastly, developers can ignore the transition between online and offline modes, resulting in longer load times, or data out-of-date when connectivity is restored. The application design should have an efficient action queue of the different actions the user performed offline, for when they go back online, the data is synchronized correctly.

Summary

The core idea behind these technologies and techniques is to enable web applications to continue to function even when offline, caching essential assets and data, delivering appropriate content and syncing data with the server upon reconnection, prioritizing seamless user experience, all of this regardless of the connectivity or device used by the user.