I. Executive Summary: The State of Mobile-Desktop Convergence

As of October 2025, the mobile external display market is at a profound inflection point, defined by disruption, fragmentation, and imminent competition. This report analyzes the current landscape for phones supporting both "mirror" and "extended" desktop modes across the Android and iOS ecosystems. The "Windows" portion of the query will be addressed as a historical postmortem, as the Windows Phone platform is defunct.

The market is currently defined by three developments:

• The "Great Regression" of Samsung DeX: The long-standing gold standard for mobile desktops is in a state of crisis. The recent One UI 8 update, built on Android 16, has introduced significant feature regressions and usability bugs, alienating its core prosumer base.
• The "Nascent Future" of Native Android: Google has finally embraced hardware video-out with its Pixel 10 line. However, its new native "Desktop Mode" in Android 16 remains a buggy, developer-focused beta, defaulting to basic mirroring out of the box.
• The "Imminent Threat" from Apple: The iOS ecosystem, currently limited to basic screen mirroring, is poised to enter the extended desktop race. Persistent rumors point to a "Stage Manager" feature arriving for the iPhone in 2026 with iOS 19.

The choice for prosumers is no longer simple. This report will dissect the technical foundations, analyze the fragmented state of the Android ecosystem, clarify the "mirror-only" limitations of iOS, and provide a compatibility guide for all major 2024-2025 devices.

II. Defining the Experience: Mirror vs. Extended

A. Level 1: Screen Mirroring (The Baseline)

Screen mirroring is the most basic form of external display support. It functions as a direct, 1:1 duplication of the phone's screen onto an external monitor. This is the default behavior for all modern USB-C iPhones and new Google Pixel phones when first plugged in.

This mode is functionally limited by the "Black Bar Problem." Phone screens (e.g., 19.5:9 ratio) do not match standard 16:9 monitors. This mismatch results in "pillarboxing" (black bars on the sides), wasting screen real estate and creating a subpar experience for anything other than video.

B. Level 2: Extended Desktop Mode (The Productivity Goal)

Extended Desktop Mode is the true "phone-as-a-PC" solution. This technology transforms the phone into the "brain" of a computer, displaying a separate, PC-like desktop environment (with a taskbar, app drawer, and icons) on the external monitor. The phone's screen remains independently usable, often serving as a trackpad.

The core features are true multi-windowing, the ability to freely resize and snap app windows, and full support for an external mouse and keyboard. This is the functionality delivered by platforms like Samsung DeX and Motorola's Smart Connect.

III. The Technology Explained: Hardware vs. Software

C. The Hardware Foundation: DisplayPort Alt Mode (DP Alt Mode)

For a high-performance, low-latency wired connection, a hardware feature called DisplayPort Alternate Mode (DP Alt Mode) is essential. This specification allows a device's USB-C port to transmit a native DisplayPort video signal.

This feature is a primary differentiator between flagship and mid-range phones. To cut costs, budget and mid-range devices omit this hardware-level capability, making them physically incapable of *any* wired video output.

A common point of confusion is USB data speed. For example, the base-model iPhone 15 has a USB 2.0 *data speed* port (480 Mbps). However, this port *still supports* DP Alt Mode because the high-speed video signal uses separate, dedicated wires within the USB-C connector, independent of the low-speed data wires.

D. The Software-Based Solution: DisplayLink Technology

DisplayLink is a technology that functions as a workaround for devices lacking native DP Alt Mode. It uses a special chipset inside a dock or adapter to compress video data and send it over a standard USB data connection. This is the *only* way a device like an older Pixel 7 can output to a monitor.

DisplayLink also serves as an *advanced* solution. For instance, a Google Pixel 9 (which has DP Alt Mode) can use a DisplayLink Pro dock to drive *two* independent external displays simultaneously—a feat even Samsung DeX cannot accomplish.

IV. The Android Ecosystem: A Landscape of Competing Visions

A. Samsung DeX: The Champion in Crisis

For years, Samsung DeX was the undisputed leader. As of October 2025, however, the DeX platform is in turmoil. The new Android 16 / One UI 8 update, shipping on the Galaxy S25 series, represents a strategic *merger* of Samsung's proprietary codebase with Google's new, native Android 16 Desktop Mode framework.

The immediate consequence is that the new DeX has *inherited all of its v1.0 limitations*. The current user experience on the latest S25 devices is described by beta users as "almost completely broken."

Key regressions reported by users of One UI 8 include:

• Broken Window Management: DeX no longer remembers app window sizes or positions, forcing users to resize *every app, every time* it is opened.
• UI Scaling Bugs: At high resolutions (3K or 4K), the DeX taskbar and app menu do not scale, remaining "super-tiny" and unusable.
• Broken Touch Input: On touch-screen devices, touch input for resizing or moving windows is non-functional, making the interface dependent on a mouse.

B. Google's Native Android 16 Desktop Mode: The Nascent Future

After years of omitting DP Alt Mode from its flagships, Google has pivoted. The Pixel 9 and new Pixel 10 series now support native video output.

The software, however, is in its infancy. The new native Desktop Mode in Android 16 is not a consumer-ready feature. When a new Pixel 10 is connected, it *still defaults to mirror mode*. To activate the extended desktop, a user must navigate into the hidden Developer Settings and manually "Enable desktop experience features."

When enabled, this beta-quality feature is plagued by limitations:

• Low Resolution: Users report a "very low" resolution output, with "blurry and pixelated" icons and text.
• Broken UI: Key interface elements, such as the notification panel and Quick Settings, are not yet functional.
• Poor Input Handling: A lack of "pointer lock" support in browsers makes cloud gaming services unusable.

C. Motorola Smart Connect: The Versatile Contender

Motorola's "Ready For" platform has been rebranded and expanded into "Smart Connect." This platform is available on recent flagship Motorola Edge and Razr devices.

In the shadow of DeX, Smart Connect has built a loyal following. It offers a "Mobile Desktop" but also includes several features DeX lacks, such as cross-platform interoperability with Windows PCs and tablets, superior wireless performance, and versatile modes for gaming or streaming.

V. The iOS Ecosystem: On the Cusp of a Revolution

A. Current State (iOS 18): Locked to Mirror Mode

The iOS ecosystem's current external display support is primitive. All USB-C iPhones—including the iPhone 15, 16, and new 17 series—support wired video output via DP Alt Mode. The limitation is purely software-based.

As of October 2025, iOS 18 *only* permits screen mirroring. This mirror-only state is functionally poor for productivity, as it is plagued by the "Black Bar" aspect ratio problem.

B. Future Trajectory (The iOS 19 Rumor): "Stage Manager" for iPhone

A persistent and credible rumor claims that iOS 19 will introduce a "Stage Manager-like" extended desktop interface for the iPhone. This update is expected to be announced at WWDC in June 2026 and released in the fall.

This would not be a full macOS experience but a multi-app, windowed environment on the external display, similar to what is available on M-series iPads. It is highly probable that Apple will lock this new feature to the "Pro" models (e.g., iPhone 17 Pro and Pro Max).

VI. The Windows Phone Ecosystem: A Concluded History

VII. 2025 Device Compatibility Guide and Comparative Matrix

The 2025 Market Divide

The market is starkly divided. Flagship devices from Samsung, Google, and Apple all *possess the required DP Alt Mode hardware*. The differentiation is *purely software*.

Mid-range devices are the "budget trap." To hit their aggressive price points, phones like the Google Pixel 9a and Nothing Phone (3a) Pro *cut* this hardware. These phones will *not* support any wired video output, a major disappointment for buyers who assume all USB-C ports are created equal.

VIII. Strategic Recommendations and Future Outlook (2026-2027)

A. Recommendation for Power Users (Oct 2025)

The "best" choice for a mobile desktop is currently compromised. Purchasing the *newest* flagship device (Galaxy S25 or Pixel 10) for this purpose is paradoxically a *worse* experience *today* than buying last-generation's Galaxy S24 or a current Motorola Edge.

• For Maximum Stability Today: Purchase a Samsung Galaxy S24 Ultra and *decline* the One UI 8 update, or purchase a Motorola Edge 60 Pro. These offer the most stable desktop experiences.
• For Future-Proofing (The Gamble): Purchase a Google Pixel 10 Pro. This is a bet on Google's ecosystem. The desktop mode is functionally poor today but will (presumably) improve.
• The Patient User: Wait 6-8 months. This provides time to see if Samsung patches the DeX regressions and if Apple's iOS 19 "Stage Manager" rumor materializes.

B. Forward Outlook (2026-2027)

The market is in a temporary trough. By 2027, a new, stable, three-way race is expected to emerge:

• Google: A mature and stable Native Android Desktop Mode.
• Samsung: A "re-matured" DeX, having adapted to the native Android framework.
• Apple: A powerful "Stage Manager for iPhone," likely restricted to Pro-series phones, which will place immense pressure on Android app quality.