iPhone Duo Reviews Report Excessive Heat and Performance Lag

Multiple technology reviewers reported that the new iPhone Duo generates significant heat during intensive tasks, leading to performance reductions and user discomfort.

How it unfolded

• Joanna Stern of CNN reported the device back became warm during FaceTime and photo capture, forcing her to end a call due to excessive heat.
• The Verge noted the phone heats up during long camera sessions, especially with Duo Preview active, causing noticeable lag after a period of use.
• PetaPixel observed warmth on the right side of the unfolded device during gaming, photo editing, and other processor-stressing activities.
• Mrwhosetheboss conducted a stress test showing the iPhone Duo trapped heat when closed, resulting in performance below the iPhone 18 Pro Max.
• HTX Studio recorded the iPhone Duo at 46.5°C during a 30-minute gaming test, compared to 43.8°C for the iPhone 18 Pro and 43.2°C for the Pro Max.

Who is affected

Users who engage in sustained high-performance activities on the iPhone Duo are most likely to experience these thermal issues. According to The Verge, running third-party applications, particularly video apps and those from Google, also triggers heating. The device’s thermal behavior impacts users relying on both displays simultaneously for features like Duo Preview. While some reviewers found the device only warm, others described it as running too hot at times, affecting the overall user experience during demanding tasks.

What happens next

Apple explained to Joanna Stern that the warmth is a sign of the iPhone Duo’s thermal design moving heat away from the chip to maintain performance. The device uses a custom vapor chamber setup and A20 Pro chip, similar to the iPhone 18 Pro, but with a thinner vapor chamber. Apple added a flexible graphite pipe in the hinge to transfer heat between the two halves, increasing surface area for dissipation. Users may need to manage their usage patterns to avoid overheating, as no software fix has been confirmed yet.

The background in plain language

Modern smartphones use complex cooling systems to manage heat from powerful processors. When devices get hot, they may slow down to protect internal components, leading to lag or reduced brightness. Foldable phones face unique challenges because their compact design limits space for traditional cooling methods. Manufacturers often use materials like vapor chambers and graphite to spread heat across larger surfaces. Understanding these thermal dynamics helps users recognize why certain tasks cause devices to warm up and how design choices impact performance and comfort.

What to do and how to stay safe: iPhone Duo

• Monitor device temperature during intensive tasks like gaming or video editing to avoid prolonged exposure to heat.
• Avoid using the device while it is charging if you notice it becoming unusually warm, as this can exacerbate thermal issues.
• Close unused applications and reduce screen brightness to lessen the load on the processor and manage heat generation.
• Ensure the device is not covered or placed in environments that restrict airflow, allowing heat to dissipate more effectively.

Step-by-step guide: Mobile Device Security for Small Business: Control Without Cost

General security guidance from the Circuit Observer newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

Why does the iPhone Duo get hot during use?

The iPhone Duo generates heat during intensive tasks due to its powerful processor and limited cooling space, with Apple stating the warmth helps move heat away from the chip.

Does the iPhone Duo perform worse than the iPhone 18 Pro?

Yes, in stress tests, the iPhone Duo showed lower frame rates and brightness levels compared to the iPhone 18 Pro and Pro Max models.

Is there a fix for the overheating issue?

No fix has been confirmed yet, as Apple has not released any software updates or patches addressing the thermal concerns reported by reviewers.