For mobile users who have grown accustomed to the frustrating unpredictability of VPN applications, the notion of a connection that remains steadfastly stable without unexpected crashes or disconnects often seems more like a distant dream than an achievable reality. In a decisive move to turn this expectation into a standard feature, Mullvad VPN has executed a fundamental re-engineering of its service’s core, introducing a custom-built WireGuard engine designed to deliver unprecedented reliability and performance. This strategic pivot is not merely an incremental update but a foundational shift that addresses the deep-seated causes of instability, setting a new benchmark for what users can expect from their privacy tools.
What if 85% of Your App Crashes Could Simply Vanish
The persistent annoyance of application instability is a well-known issue for many VPN users, particularly on mobile devices where network conditions fluctuate and software conflicts are common. An abrupt disconnection during a critical task or a random crash can undermine the very sense of security and reliability a VPN is meant to provide. For a long time, these minor but frequent interruptions were often dismissed as an unavoidable cost of using such complex software on dynamic operating systems, a hidden friction that users were forced to tolerate.
Mullvad’s internal diagnostics, however, painted a much clearer picture, revealing that this was not a random or unsolvable problem. An extensive analysis traced over 85% of all reported application crashes on its Android platform to a single, identifiable source. Confronted with this data, the company recognized an opportunity for a transformative solution. Instead of patching the symptoms, it pursued a complete architectural overhaul aimed at eliminating the root cause, proposing a fundamental change that promised to deliver near-perfect operational stability.
The Root of the Problem a Clash of Code
The core of the instability issue resided in the previous engine, “wireguard-go,” a widely used implementation of the WireGuard protocol. While functional, its underlying codebase presented a significant challenge. Written in the Go programming language, the engine was technically at odds with the rest of Mullvad’s application infrastructure, which is built predominantly with the Rust programming language. This mismatch created a persistent state of conflict within the software’s architecture.
This technical friction was more than just an abstract engineering problem; it had tangible and disruptive consequences for the end-user. The clash between the Go and Rust codebases manifested as frequent application crashes, unpredictable behavior, and a generally degraded user experience. These problems were particularly pronounced on Android, where the operating system’s process management would often magnify the underlying instability, leading to a service that felt unreliable and cumbersome.
GotaTun Mullvads Custom Built WireGuard Engine
In response to these challenges, Mullvad developed “GotaTun,” its own custom WireGuard engine built entirely in Rust. The project, which was forked from Cloudflare’s highly respected “BoringTun” implementation, was engineered for seamless integration with Mullvad’s existing Rust-based systems. This native compatibility eliminates the core conflict that plagued the previous engine, creating a unified and cohesive software environment.
The results of this transition have been nothing short of revolutionary. Since GotaTun was deployed to Android users in late 2025, the user-perceived crash rate has plummeted from 0.40% to an almost imperceptible 0.01%. More significantly, internal logs show that zero crashes have been directly attributed to the new engine, validating the architectural change. This dramatic improvement in stability transforms the user experience from one of tolerance to one of trust and reliability.
Furthermore, the benefits of GotaTun extend beyond just crash reduction. The inherent advantages of the Rust language, specifically its guarantees of “memory safety” and its use of “zero-copy” strategies for data handling, translate directly into performance gains. These features allow for more efficient data processing, resulting in faster connection speeds and lower CPU usage. For mobile users, this efficiency provides a significant and welcome side effect: reduced battery consumption, allowing their devices to stay connected longer without draining power.
Vetting the Upgrade and Aligning with an Industry Wide Shift
Mullvad’s strategic adoption of Rust is not an isolated decision but rather part of a broader, industry-wide trend toward using the language for developing high-performance, security-critical applications. Rust’s design provides robust protections against common memory-related vulnerabilities that have historically plagued software written in other languages. This shift is mirrored by other key players in the privacy space, such as ExpressVPN’s development of its own Lightway protocol, which similarly leverages modern technologies to enhance security and speed.
Reinforcing its long-standing commitment to transparency and user trust, Mullvad has also committed to subjecting the new GotaTun code to a comprehensive third-party security audit. This independent verification, scheduled for early this year, will provide an external assessment of the engine’s security posture. By inviting expert scrutiny, the company aims to offer its users verifiable assurance that the new implementation not only performs better but also upholds the highest standards of digital security.
What This Means for Mullvad Users a Look Ahead
This technological leap is a cornerstone of Mullvad’s larger strategy to consolidate its service around a single, superior protocol. With the successful deployment of GotaTun, the company officially phased out support for the older OpenVPN protocol on January 15, 2026. This move allows the development team to focus all its resources on optimizing and innovating within the WireGuard ecosystem, ensuring a more streamlined, secure, and future-proof service for all users.
The deployment of the new engine is continuing throughout the year. While GotaTun has already demonstrated its capabilities on the Android platform, Mullvad is actively working to integrate it across its entire suite of applications. The planned rollout will see the new engine implemented on all desktop and iOS clients in 2026, bringing the same standard of stability and performance to every user, regardless of their preferred device.
Beyond the immediate performance improvements, the GotaTun engine unlocks advanced privacy features from day one. Its modern architecture was designed with out-of-the-box support for sophisticated tools like Multihop and Dynamic Advanced Internet Traffic Analysis (DAITA). These features enable users to route their traffic through multiple VPN servers, providing an additional layer of protection against traffic analysis and strengthening their online anonymity in an increasingly monitored digital landscape.
The introduction of GotaTun was far more than a simple bug fix; it represented a complete re-evaluation of how a VPN service should be constructed for the modern era. By replacing a problematic component with a custom-built solution, Mullvad not only resolved a critical stability issue but also laid a new foundation for future innovation. This decisive action underscored a commitment to engineering excellence and user experience, ultimately delivering a service that was faster, more stable, and better equipped to protect user privacy.
