Best custom firmware for retro handhelds in 2025

Custom firmware is what separates a good retro handheld from a great one. Stock firmware on most budget devices is rough — laggy menus, no artwork, outdated emulators. The right custom firmware fixes all of that. Here’s a complete breakdown of every major option in 2025.

Quick decision guide

What device do you have?

Device	Best firmware	Runner-up
Miyoo Mini Plus	OnionOS	MinUI
Miyoo Flip	OnionOS	MinUI
Anbernic RG35XX H	KNULLI	GarlicOS
Anbernic RG28XX	KNULLI	MinUI
TRIMUI Smart Pro	KNULLI	Stock
Anbernic RG405M	ROCKNIX	Stock Android
Anbernic RG Cube	ROCKNIX	Stock Android
AYN Odin 2 Mini	ROCKNIX	Stock Android
Retroid Pocket 5	RetroArch + Daijishō	—

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The full comparison

	OnionOS	GarlicOS	KNULLI	MinUI	ROCKNIX
Based on	Custom Linux	Custom Linux	Batocera	Custom Linux	Immutable Linux
Device support	Miyoo only	Anbernic H700	Anbernic + TRIMUI	Miyoo + Anbernic	Anbernic + AYN
UI quality	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐	⭐⭐ (minimal)	⭐⭐⭐⭐
RetroAchievements	✅	✅	✅	❌	✅
Wi-Fi features	✅	❌	✅	❌	✅
Artwork scraping	✅	❌	✅	❌	✅
Battery life	Good	⭐ Excellent	Good	⭐ Excellent	Good
Boot speed	~15s	~8s	~20s	~6s	~25s
Beginner-friendly	✅	✅	✅	⚠️ Minimal	⚠️ Complex
Latest version	v4.3.1-1	v2.0.0	20250813	20251127-1	20250517
Update frequency	Monthly	Slow	Regular	Regular	Regular

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OnionOS — best for Miyoo devices

OnionOS is the most polished custom firmware available for any retro handheld. Built specifically for the Miyoo Mini Plus and Miyoo Flip, it delivers a premium experience that makes the $59 Miyoo Mini Plus feel like a $150 device.

Highlights:

• Beautiful, themeable UI with a large community theme library
• RetroAchievements built in — earn achievements in classic games
• Wi-Fi artwork scraping — automatic box art and screenshots
• Package manager for easy emulator and app updates
• Instant sleep/resume — pick up exactly where you left off

Best for: Anyone with a Miyoo Mini Plus or Miyoo Flip. It’s the #1 reason these devices are so popular.

👉 OnionOS firmware tracker & download → | Installation guide →

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KNULLI — best for Anbernic & TRIMUI devices

KNULLI is the most feature-complete option for Anbernic H700 devices (RG35XX H, RG28XX) and the TRIMUI Smart Pro. Based on Batocera Linux, it brings a mature, well-tested foundation with extensive emulator support.

Highlights:

• Supports RG35XX H, RG28XX, and TRIMUI Smart Pro in one firmware
• Batocera-based: proven, stable, and regularly updated
• RetroAchievements, Wi-Fi artwork scraping, network play
• Clean EmulationStation-style UI
• Active development team with regular releases

Best for: Anbernic or TRIMUI device owners who want a full-featured experience comparable to OnionOS.

👉 KNULLI firmware tracker & download →

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GarlicOS — lightweight & fast

GarlicOS prioritizes speed and battery life above all else. It’s built for Anbernic H700 devices and strips away everything non-essential.

Highlights:

• Boots in ~8 seconds — noticeably faster than alternatives
• Best-in-class battery life for Anbernic devices
• Simple, clean interface — no clutter
• Well-tuned RetroArch configuration out of the box
• Stable and reliable

Best for: RG35XX H or RG28XX owners who want maximum battery life and a no-fuss experience. If you don’t need Wi-Fi features or artwork, GarlicOS is excellent.

👉 GarlicOS firmware tracker & download → | GarlicOS vs OnionOS comparison →

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MinUI — for minimalists

MinUI is the most minimal firmware available. No artwork, no themes, no settings menus — just a clean black-and-white list of your games. It supports both Miyoo and Anbernic devices, making it the most versatile option.

Highlights:

• Supports Miyoo Mini Plus, Miyoo Flip, RG35XX H, and RG28XX
• Fastest boot time of any firmware (~6 seconds)
• Best battery life across all supported devices
• Zero visual clutter — pure focus on playing games
• Surprisingly capable emulation despite the minimal footprint

Best for: Users who hate menus and just want to play games. Also great as a secondary firmware on a spare SD card.

👉 MinUI firmware tracker & download →

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ROCKNIX — for powerful Android-capable devices

ROCKNIX is a community-developed immutable Linux distribution targeting more powerful devices: the RG405M, RG Cube, and AYN Odin 2 Mini. It’s a fork of JELOS with a focus on performance and stability.

Highlights:

• Supports RG405M, RG Cube, and AYN Odin 2 Mini
• Immutable OS design — more stable and harder to break
• Excellent performance on powerful hardware
• Active community development
• Good PS2 and GameCube emulation on supported devices

Best for: Owners of more powerful Anbernic or AYN devices who want a Linux-based alternative to stock Android.

👉 ROCKNIX firmware tracker & download →

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What about stock firmware?

For Android-based devices like the Retroid Pocket 5 and AYN Odin 2 Mini, stock Android is actually a reasonable choice — you get access to the Play Store, standalone emulators like AetherSX2 and Dolphin, and a familiar interface. Pair it with RetroArch and a frontend like Daijishō for the best experience.

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How to choose

Step 1: What device do you have?

• Miyoo Mini Plus / Miyoo Flip → OnionOS (or MinUI for minimalists)
• Anbernic RG35XX H / RG28XX → KNULLI (features) or GarlicOS (speed/battery)
• TRIMUI Smart Pro → KNULLI
• RG405M / RG Cube / AYN Odin 2 Mini → ROCKNIX or stock Android
• Retroid Pocket 5 → Stock Android + RetroArch

Step 2: What do you value most?

• Best UI and features → OnionOS or KNULLI
• Best battery life → GarlicOS or MinUI
• Simplest experience → MinUI
• Most device support → MinUI (Miyoo + Anbernic)

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Stay updated

Custom firmware moves fast. Use our Firmware Tracker to monitor all major projects — latest versions, changelogs, and download links in one place.

Related reading

• What is custom firmware? — beginner overview
• How to install OnionOS — step-by-step guide
• GarlicOS vs OnionOS — detailed comparison
• Best retro handhelds in 2025 — device picks