ButterKit

ButterKit is a native macOS application purpose-built for Apple developers who need to streamline the complex and time-consuming process of creating, localizing, and publishing App Store screenshots and metadata. Serving thousands of developers, design studios, and marketing agencies worldwide, ButterKit addresses a critical pain point: the manual effort required to produce polished, localized App Store assets often causes developers to skip localization entirely, missing out on valuable organic search traffic in international markets. The product integrates directly with Xcode Simulator for capturing screenshots, places them into photorealistic 3D device frames rendered on Apple Silicon via Metal for up to 120fps performance, and provides instant translation into all 50 App Store Connect languages using frontier AI models or 18 languages for free using on-device Apple Silicon. Beyond design and translation, ButterKit enables direct upload to App Store Connect via its API, supports folder linking for seamless integration with Fastlane and CI/CD pipelines, and offers MCP support so AI coding tools can automate the entire workflow. Built by a solo developer for developers who ship, ButterKit transforms a tedious manual process into a smooth, automated pipeline.

Capture from Xcode Simulator or Drag and Drop

ButterKit eliminates the friction of screenshot preparation by offering two powerful capture methods. You can drag and drop PNG or JPG screenshot images directly onto 3D device frames, and the application instantly renders them in photorealistic quality. Alternatively, the Capture Tool integrates directly with Xcode and Simulator, allowing you to capture screenshots from your running app without leaving the development environment. This tight integration saves significant time compared to web-based tools and enables rapid iteration to achieve the exact visual design you need.

Real 3D Device Rendering Engine

Unlike flat mockup generators, ButterKit is a powerful 3D rendering engine built on Apple's Metal framework. It includes high-resolution, photorealistic 3D device frames that you can rotate, scale, and position to create the most compelling presentation for your app. Edits are exceptionally fast, running at up to 120fps on Apple Silicon hardware. You can span 3D devices across multiple artboards and create seamless panoramic backgrounds that tie your entire screenshot set together, delivering a cohesive visual story for your App Store listing.

Instant Translation to 50 Languages

ButterKit directly addresses the localization gap that plagues many App Store listings. Using frontier AI models (with your own API key) or on-device Apple Silicon for 18 free languages, you can translate both screenshots and app metadata into all 50 App Store Connect localizations in seconds. Critically, your design layouts stay perfectly synced across every language, so you do not need to manually reposition text or adjust artboards. This feature ensures your app appears in native language search results across every market Apple supports.

Seamless CI/CD and Fastlane Integration

ButterKit is designed to fit naturally into automated development workflows. You can link entire folders of images for both input and output, making it a natural companion for Fastlane and CI/CD pipelines. Combined with MCP support that allows AI coding tools to control the application programmatically, ButterKit enables fully automated screenshot generation, translation, and publishing. This means your entire App Store asset pipeline can run without manual intervention, from code commit to live listing update.

Indie Developer App Store Optimization

Independent developers often lack the resources to create localized App Store assets for every market. With ButterKit, a solo developer can capture screenshots from their Xcode project, apply a professional template, translate everything into 50 languages using on-device AI, and upload directly to App Store Connect in under an hour. This dramatically increases the app's visibility in international search results without requiring a localization team or hours of manual design work.

Design Studio Client Deliverables

Design studios and marketing agencies managing multiple App Store listings for clients can leverage ButterKit's template system and batch processing capabilities. The ability to create a master design, apply it across multiple client apps, and instantly generate localized versions for each client's target markets streamlines what would otherwise be a repetitive, error-prone process. The direct upload feature also eliminates the back-and-forth of exporting and manually uploading assets.

Enterprise App Localization Teams

Large enterprises with apps distributed across dozens of countries can use ButterKit as the central hub for their App Store asset pipeline. By integrating with existing CI/CD workflows via folder linking and Fastlane, enterprise teams can ensure that every app update triggers automatic screenshot regeneration and translation. The MCP support further allows custom automation scripts to control the entire publishing process, reducing the risk of human error and ensuring consistency across all localizations.

Iterative A/B Testing for Conversion Optimization

Developers who want to test different screenshot styles and messaging to improve conversion rates can use ButterKit's rapid iteration capabilities. The ability to capture directly from Simulator, apply different templates, and preview how the story will look on every device and in every language before publishing enables data-driven optimization. Users can quickly generate multiple variants, upload them to App Store Connect, and analyze which designs drive the best conversion metrics.

Does ButterKit require a subscription or is it a one-time purchase?

ButterKit is a native macOS application available for download. The pricing model is based on a one-time purchase, not a recurring subscription. This makes it a cost-effective investment for developers who need ongoing access to professional screenshot creation and localization tools without monthly fees.

How does the translation feature work with my own API key?

ButterKit supports frontier AI models for translation when you bring your own API key from providers like OpenAI or Anthropic. This gives you control over which model is used, your data privacy, and usage costs. For users who prefer a free option, ButterKit also offers translation into 18 languages using on-device Apple Silicon processing, which keeps all data local and does not require any external API calls.

Can ButterKit integrate with my existing Fastlane setup?

Yes, ButterKit is designed to integrate seamlessly with Fastlane and other CI/CD pipelines. You can link entire folders of generated screenshots as input, and ButterKit will process them automatically. The output can also be directed to a folder, which Fastlane can then pick up for upload to App Store Connect. This makes it easy to add professional screenshot creation and localization into your automated build and deployment workflow.

What file formats and image resolutions does ButterKit support?

ButterKit supports standard image formats including PNG and JPG for input screenshots. The application is built on Metal and renders at high resolution, supporting all device sizes required by App Store Connect. Because it integrates directly with Xcode Simulator, it can capture screenshots at the exact resolution your app renders, ensuring pixel-perfect results that meet Apple's strict submission guidelines.