# Downloading and Compiling a Model on the User’s Device Install Core ML models on the user’s device dynamically at runtime. ## Discussion Download and compile models within your app as an alternative to bundling with the app. Scenarios where this is a practical approach include: - Reducing the app’s download size of your app on the App Store - Determining the right models for the user after installation based on their location, specific interests, and A/B testing - Providing model updates over the network ### Download and compile the model in the background Download the model definition file (ending in `.mlmodel`) onto the user’s device by using , , or another networking toolkit. Then compile the model definition by calling [`compileModel(at:)`](/documentation/CoreML/MLModel/compileModel(at:)-6442s). ```swift let compiledModelURL = try MLModel.compileModel(at: modelDescriptionURL) ``` This creates a new, compiled model file with the same name as the model description but ending in `.mlmodelc`. Create a new [`MLModel`](/documentation/CoreML/MLModel) instance by passing the compiled model to its initializer. ```swift let model = try MLModel(contentsOf: compiledModelURL) ``` Model instances you create from model files you’ve downloaded have the same capabilities as those you create from model files that you bundle with your app. ### Save Reusable Models to a Permanent Location [`MLModel`](/documentation/CoreML/MLModel) saves models it compiles to a temporary location. If your app can reuse the model later, reduce your resource consumption by saving the compiled model to a permanent location. Build the to a permanent location that your app can access in the future, such as Application Support. ```swift let fileManager = FileManager.default let appSupportURL = fileManager.urls(for: .applicationSupportDirectory, in: .userDomainMask).first! ``` Create the for the permanent compiled model file. ```swift let compiledModelName = compiledModelURL.lastPathComponentlet permanentURL = appSupportURL.appendingPathComponent(compiledModelName) ``` Move or copy the file to its permanent location. ```swift // Copy the file to the permanent location, replacing it if necessary. _ = try fileManager.replaceItemAt(permanentURL, withItemAt: compiledModelURL) ``` > Important: > You should consider the user’s iCloud Backup size when saving large, compiled Core ML models. You can store models in the app’s container using /tmp and /Library/Caches directories, which contain purgeable data that isn’t backed up. When the models aren’t purgeable, you can exclude them from backup by setting the resource value to `true`. To learn more about excluding files from iCloud Backup, see . --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)