Network.framework API Reference

Overview

Network.framework is Apple's modern networking API that replaces Berkeley sockets, providing smart connection establishment, user-space networking, built-in TLS support, and seamless mobility. Introduced in iOS 12 (2018) with NWConnection and evolved in iOS 26 (2025) with NetworkConnection for structured concurrency.

Evolution timeline

• 2018 (iOS 12) NWConnection with completion handlers, deprecates CFSocket/NSStream/SCNetworkReachability
• 2019 (iOS 13) User-space networking (30% CPU reduction), TLS 1.3 default
• 2025 (iOS 26) NetworkConnection with async/await, TLV framing built-in, Coder protocol, Wi-Fi Aware discovery

Key capabilities

• Smart connection establishment Happy Eyeballs (IPv4/IPv6 racing), proxy evaluation (PAC), VPN detection, WiFi Assist fallback
• User-space networking ~30% lower CPU usage vs sockets, memory-mapped regions, reduced context switches
• Built-in security TLS 1.3 by default, DTLS for UDP, certificate pinning support
• Mobility Automatic network transition handling (WiFi ↔ cellular), viability notifications, Multipath TCP
• Performance ECN (Explicit Congestion Notification), service class marking, TCP Fast Open, UDP batching

When to use vs URLSession