Universal Binary
A macOS application bundle that contains native compiled code for both Apple Silicon (ARM64) and Intel (x86_64) architectures, running natively on either processor without emulation.
Apple introduced Universal Binary 2 with the transition from Intel processors to Apple Silicon (M-series) chips beginning in 2020. A Universal Binary app bundle contains two compiled versions of the code — one for ARM64 (Apple Silicon) and one for x86_64 (Intel) — merged into a single download. When the user launches the app, macOS automatically selects the correct binary for the machine's processor.
Apps that are not Universal Binaries but include only Intel (x86_64) code run on Apple Silicon Macs through Rosetta 2, Apple's translation layer. Rosetta 2 is transparent and reasonably fast, but a native ARM64 build offers better performance and lower energy consumption, which matters for processing-intensive tasks like parsing large MBOX files.
Mbox Viewer is distributed as a Universal Binary, meaning it runs natively on both Apple Silicon and Intel Macs without requiring Rosetta 2. Users on either architecture get the full native performance of their hardware.
Related terms
App Sandbox is a macOS security feature that restricts an application's access to system resources, files, and network connections, limiting the potential impact if the app or its dependencies have a vulnerability.
A parsing technique that reads a file incrementally in small chunks rather than loading the entire file into memory at once, enabling tools to open and index very large MBOX files — tens or hundreds of gigabytes — with low memory usage.