Kingfisher/Sources/Documentation.docc/Topics/Topic_LowDataMode.md

Low Data Mode

Loading image and customizing behaviors for the Low Data Mode.

Overview

Starting with iOS 13, Apple has introduced the option for users to enable Low Data Mode to reduce cellular and Wi-Fi data usage. To accommodate this setting, you can offer an alternative version of your image, typically in lower resolution. Kingfisher will automatically switch to this version when Low Data Mode is activated, helping to conserve data.

imageView.kf.setImage(
    with: highResolutionURL, 
    options: [.lowDataSource(.network(lowResolutionURL)]
)

In the scenario described, if the user has not applied any network restrictions, the highResolutionURL will be utilized for fetching the image. However, if the device is in Low Data Mode and the highResolutionURL version is not found in the cache, the lowResolutionURL will be selected as the fallback option to save data.

Given that the .lowDataSource option accepts any Source parameter, not just a URL, you have the flexibility to pass in a local image provider. This approach effectively eliminates the need for a downloading task, allowing for the use of locally stored images when operating under Low Data Mode or other restrictive network conditions.

imageView.kf.setImage(
    with: highResolutionURL, 
    options: [
        .lowDataSource(
            .provider(LocalFileImageDataProvider(fileURL: localFileURL))
        )
    ]
)

For more about this topic, check doc:Topic_ImageDataProvider and ImageDataProvider documentation.

tip: If the .lowDataSource option is not specified, the highResolutionURL will be used by default, regardless of the Low Data Mode setting on the device.