1. Build Script Language: The primary difference between Gradle and fastlane lies in their build script languages. Gradle uses a powerful and flexible language called Groovy, which allows developers to write highly expressive and customizable build scripts. On the other hand, fastlane utilizes a configuration-based approach with a domain-specific language (DSL), which simplifies the build process by abstracting away complex logic and providing predefined actions for common tasks.

2. Platform Compatibility: Another notable difference between Gradle and fastlane is their platform compatibility. Gradle is a versatile build tool that is widely compatible with various platforms, including Android, iOS, and web. It offers extensive support for cross-platform development and can be easily integrated into existing build pipelines. In contrast, fastlane is primarily focused on iOS and Android app development, providing a streamlined workflow for automating various tasks specific to mobile application development.

3. Community and Ecosystem: Gradle boasts a large and vibrant community, supported by the Gradle build ecosystem. It offers a rich set of plugins and extensions that can be leveraged to enhance the build process, integrate with other tools, and customize workflows according to specific project requirements. Fastlane also has a strong community support but is relatively more focused on mobile application development, with a dedicated community of developers and a vast array of pre-built plugins specifically tailored for iOS and Android automation.

4. Integration with App Stores: One significant difference between Gradle and fastlane lies in their integration with app stores. Gradle provides native support for publishing Android apps to the Google Play Store, allowing developers to automate the deployment process seamlessly. Fastlane, on the other hand, is specifically designed to simplify the release process of iOS and Android apps. It provides integrated actions for automating app store submissions, managing certificates and provisioning profiles, and handling code signing for streamlined app deployment.

5. Plugin and Dependency Management: Gradle excels in its ability to manage project dependencies efficiently. It integrates seamlessly with popular dependency management systems like Maven and Ivy, allowing developers to easily incorporate external libraries and frameworks into their projects. Fastlane, while not focused on dependency management like Gradle, provides a set of actions and plugins to handle specific tasks related to mobile app automation, such as managing code signing certificates, publishing releases to app stores, running quality checks, and generating screenshots.

6. Project Configurability: Gradle offers extensive configurability, allowing developers to customize the build process to meet specific project requirements. It provides a declarative approach to define tasks and workflows, enabling developers to define complex build logic using Groovy's expressive syntax. In contrast, fastlane promotes a convention-over-configuration approach, simplifying and standardizing the build process for iOS and Android apps. It encourages developers to follow predefined conventions and workflows, reducing the need for extensive configuration.

In Summary, Gradle and fastlane differ in terms of build script language, platform compatibility, community and ecosystem, integration with app stores, plugin and dependency management, and project configurability. These differences cater to specific development needs and serve as deciding factors when choosing between the two tools.