Most budget retro handhelds work well enough out of the box, but the stock software is usually the weakest part. A custom OS replaces it with community-built firmware that is more stable, easier to theme and better tuned for each emulator. Which one you should use depends on the chip inside your handheld: ArkOS-family builds for the R36S, Knulli for Anbernic's H700 models, CrossMix for TrimUI, Onion for Miyoo, ROCKNIX for RK3566 devices, and ES-DE as a frontend on Android.
This guide replaces our 2024 manuals. The project status notes below were checked against each project's official pages and release notes as of October 2026.
Quick pick: which OS for which handheld
| Device | Chip | Recommended OS |
|---|---|---|
| R36S, R36S Plus, R36H | RK3326 | ArkOS community forks (dArkOSRE, ArkOS4Clone) |
| ANBERNIC RG35XX (2024), RG35XXSP, RG40XX H and RG40XX V | Allwinner H700 | Knulli (muOS is a solid alternative) |
| TrimUI Brick Pro and other TrimUI models | Allwinner A133 family | CrossMix |
| Miyoo Mini Flip | SigmaStar SSD202D | Onion OS (Flip-compatible build) |
| R46S and similar RK3566 handhelds | RK3566 | ROCKNIX (successor to JELOS) |
| Retroid handhelds, e.g. Retroid Pocket 6 | Snapdragon | Android + ES-DE frontend |
| AYN handhelds, e.g. AYN Thor | Snapdragon | Android + ES-DE frontend |
| Mangmi Android handhelds | Snapdragon | Android + ES-DE frontend |
What is a custom OS, and why switch?
On a Linux retro handheld, the "OS" lives on the microSD card. Swap the card and you've swapped the whole system. Your device doesn't change, and you can go back to stock by putting the original card back in. Custom OS projects are free, community-maintained firmware built for specific chips. Most use RetroArch and standalone emulators under a friendlier menu. People switch for a few reasons:
- Stability. Stock cards on budget devices are often cheap, quickly assembled images. Community builds get bug fixes, kernel updates and better power management.
- Save states and resume. You can quick-save anywhere and resume when you open the lid or wake the device, which helps on a jeepney or MRT ride.
- Themes. Most custom OSes let you install new themes, icon packs and box art layouts from built-in menus.
- RetroAchievements. On Wi-Fi models, Knulli, ROCKNIX, ArkOS forks and others support RetroAchievements. You sign in once and unlock achievements in classic games.
- Better emulator configs. Per-system defaults like correct aspect ratios, shaders, overlays and hotkeys are already set. Demanding systems often get better-tuned standalone emulators.
The trade-off is that custom firmware is a hobby project. Updates can change menus, a major release sometimes needs a fresh flash, and support is matched to exact hardware revisions.
ArkOS and its forks (R36S, R36S Plus, R36H)
Targets: RK3326 handhelds, especially the R36S and its many clones.
Status: The original ArkOS project by christianhaitian was archived on GitHub on December 30, 2025, and is now read-only. Development has moved to community forks:
- dArkOSRE-R36 is a customised dArkOS build for R36S units and clones. Its supported-device table is organised by motherboard ID and screen panel, with each entry marked completed, beta or untested. R36H and R36 Plus support is listed as planned, and some boards are already in beta.
- ArkOS4Clone adapts ArkOS for many unofficial R36S-style clones and publishes regular dated releases through 2026.
Key features: a fast EmulationStation menu, good performance up to PS1 and most N64 and PSP titles on RK3326, Wi-Fi on supported adapters, and plenty of themes.
The catch: R36S-type devices ship with many different internal boards and screens. Flashing an image built for the wrong board can leave you with a black screen. Your original card's boot files (the .dtb) show which board you have, so keep that card safe.
Knulli (Anbernic H700: RG35XX and RG40XX family)
Targets: Anbernic's Allwinner H700 line, including the RG35XX (2024), RG35XX SP, RG35XX Plus/H/Pro, RG40XX H, RG40XX V, RG34XX and RG CubeXX. Knulli has also added builds for TrimUI A133 devices, several RK3326 and RK3566 handhelds, and early Retroid builds.
Status: actively developed. The current major release, "Scarab" (May 2026), changed the SD card partition layout. Moving to it from an older version means reflashing, not updating in place.
Key features: Knulli is a fork of Batocera, so it has Batocera's polished menus, scrapers, per-system settings and RetroAchievements support. Scarab added Syncthing save syncing on game exit, better battery reporting and a newer RetroArch.
muOS is the other big name on H700 devices. It's lighter and more minimal, and it also supports TrimUI's Smart Pro and Brick. Both are good. Knulli is the easier choice for first-time owners.
CrossMix (TrimUI)
Targets: TrimUI's A133-based handhelds. It started on the Smart Pro and later added the Brick (both currently out of stock with us).
Status: maintained by cizia64 on GitHub. Each release names the TrimUI models it supports, so check the release notes before flashing a newer TrimUI model like the Brick Pro.
Key features: CrossMix keeps TrimUI's own interface and builds on it. It adds background, icon and overlay selectors, emulator launchers with presets, a firmware update wizard and theme support. If you like TrimUI's stock look but want better emulator setups, this is the one to use.
Onion OS (Miyoo Mini Flip)
Targets: the SigmaStar-based Miyoo family. The official Onion project lists the Miyoo Mini (currently out of stock) and Mini Plus.
Status: active. Stable releases came out in 2025, and a 4.4 beta arrived in January 2026. The Miyoo Mini Flip uses the same chip as the Mini Plus, and it runs Onion through a Flip-compatibility build. Allium, Koriki and MinUI also run on it.
Key features: Onion was built around the Mini's low 128MB of RAM. It's very quick to boot, and it has a game switcher that resumes where you left off, auto-save on power-off, play-time tracking and a large theme library. It's a good fit for 8-bit to PS1 games on a pocketable clamshell. It won't run N64 or PSP well, and the hardware is the reason.
ROCKNIX (RK3566: R46S and similar)
Targets: a wide range of devices. These include RK3566 handhelds like the R46S, Powkiddy RGB30 and Anbernic RG353 series, RK3326 devices including the R36S, and newer Snapdragon handhelds such as the Retroid Pocket 6, Retroid Pocket 5 (currently out of stock) and AYN Odin and Thor.
Status: active, with dated releases through mid-2026. ROCKNIX is the successor to JELOS, which has stopped releasing builds.
Key features: a mainline Linux kernel, a polished EmulationStation menu, standalone emulators for PSP, Dreamcast and N64, Wi-Fi and Bluetooth controllers on supported hardware, and per-device overclock and power-saving options. The R46S uses an RK3566 image built for a similar Powkiddy board, so make sure the image you flash matches your exact board.
ES-DE on Android (Retroid, AYN, Mangmi)
Android handhelds don't need a replacement OS. Android is the platform, and you install emulator apps on it. What they gain from is a frontend, and ES-DE (EmulationStation Desktop Edition) is the most popular one. It puts all your systems into one controller-friendly menu with box art and launches the right emulator app for each game.
Status: ES-DE 3.5.0 was released on September 30, 2026. On Android it's a paid app, sold through the developer's Patreon and some app stores. It's partly closed source, so get it only from the official channels.
How to swap or reflash a microSD card safely (overview)
This is a high-level outline, not a step-by-step for a specific device. Always follow the project's own install guide for your exact model.
- Back up your saves first. Copy the saves and save-state folders to a computer. For the original card, make a full image backup, not just a file copy, so hidden boot partitions are kept.
- Keep the original card. Label it and store it somewhere dry. In our humidity, a small zip bag with a silica packet helps. It's your way back to stock and the reference for which board you have.
- Use a new, good-quality card. Most crashes and corrupted saves on budget handhelds trace back to the bundled card.
- Flash with a proper imaging tool. Raspberry Pi Imager ("Use custom" image) or balenaEtcher write the OS image correctly and verify it. If Windows asks to format the card afterwards, click Cancel.
- First boot takes longer. The OS expands its partitions on first start, so leave it plugged in and don't power off mid-setup.
- Copy your saves back into the new OS's save folder, then test one game before deleting anything.
FAQ
Will flashing a custom OS void my warranty?
We can't give a single answer for every brand and situation, so please message GameCove on our chat or Facebook page before modifying your device. Swapping in a separate microSD card leaves your original card untouched, and putting it back returns the handheld to stock.
Do I need BIOS files?
Some systems do. PlayStation, Sega CD, Neo Geo and a few others need BIOS files to boot games, or to run them accurately. BIOS files are copyrighted, so the legitimate way to get them is to dump them from a console you own. We don't include or link BIOS files. Each OS's documentation lists the exact filenames and the folder they go in.
Can I use any of these OSes on any handheld?
No. Every build is made for a specific chip and often a specific board revision. An R36S image won't boot on an RG35XX, and even two "R36S" units can need different images. Check the table above or ask us before flashing.
Which is easiest for a first-time owner?
Onion on the Miyoo Mini Flip and Knulli on the RG35XX family are the most beginner-friendly. ArkOS-family builds on the R36S are easy once you have the right image for your board, and that's the hard part.
Where do I get games?
Use games you own. Back up your own cartridges and discs with a dumper, then copy the files to the card's ROMs folders.
Do I need to update my card?
No. If everything works, you can leave it. If you do update, back up your saves first. Major releases (like Knulli Scarab) may need a full reflash, not an over-the-air update.
Not sure which OS matches your device? Browse our retro handhelds and send us a message. We'll point you to the right one.