Should you replace stock firmware?
Most budget retro handhelds are much better with custom firmware. Stock firmware can be fine for a quick test, but custom firmware usually gives cleaner menus, better emulator defaults, better save handling, nicer themes, more control and fewer weird frustrations.
Keep stock firmware if...
You are testing the device for the first time, buying for a child who only needs basic play, or you do not want to touch SD cards yet.
Install custom firmware if...
You want the device to feel polished, keep saves safe, organise ROM hacks properly, add artwork, use better hotkeys, or fix rough stock menus.
What custom firmware actually improves
Cleaner game library
Better system lists, favourites, recently played games, search, artwork and less ugly menu clutter.
Better saves
More reliable save state behaviour, autosaves, resume features and easier backup paths.
Better emulator defaults
Many firmwares ship with better cores, scaling, hotkeys and performance settings than stock.
More themes
Make the device feel like yours instead of a generic bargain handheld menu.
More systems/features
Some firmware adds ports, better scraping, Wi-Fi tools, Bluetooth helpers or deeper emulator settings.
Less stock-card risk
Installing firmware on a branded card means you are not relying on the fragile card included by many sellers.
Custom firmware comparison table
| Firmware | Best for | Devices | Beginner rating | RomHaven take |
|---|---|---|---|---|
| OnionOS | Cleanest pocket setup | Miyoo Mini / Mini Plus | Very beginner friendly | The gold standard for simple, polished play. |
| muOS | Fast, simple Anbernic experience | RG35XX Plus/H/SP and related H700 devices | Friendly | Great modern choice for Anbernic players who want speed and less clutter. |
| KNULLI | Console-like frontend | Many Anbernic/handheld devices | Medium | Looks slick and powerful, but has more options to learn. |
| GarlicOS | Classic RG35XX-style setup | Original RG35XX and some newer work-in-progress builds | Depends on device | Famous name, but check compatibility for your exact model. |
| ArkOS | Feature-heavy Linux handheld setup | R36S/RK3326-type handhelds and others | Medium | Powerful, popular, but device clones and card quirks can complicate things. |
| ROCKNIX | Modern Linux handheld firmware | Selected devices | Medium | Good option for supported devices, especially if you like current Linux handheld setups. |
| MinUI | Ultra-simple menus | Selected devices | Very simple | Best if you want fewer options, not more. |
What firmware should you use?
Miyoo Mini Plus
Use OnionOS. This is the cleanest and most widely recommended setup for Miyoo. It is ideal for GBA Pokémon hacks, save states, favourites and quick resume.
Anbernic RG35XX Plus / H / SP
Start with muOS or KNULLI. muOS is cleaner and faster-feeling; KNULLI has a more console-style frontend. Both are better long-term than relying on a random stock card.
R36S
Be careful. R36S units vary by seller and clone batch. Back up the original card first, then research the exact firmware build for your screen/device version.
TrimUI Brick / Smart Pro
Stock may be fine at first. TrimUI stock software is often more usable than the worst cheap handheld firmware, so test it before replacing everything.
How to install custom firmware without making a mess
Confirm your exact model
RG35XX Plus, RG35XX H and RG35XX SP are not all the same. R36S clone batches can differ too. Match the guide to the exact device.
Back up the original SD card
Copy everything to your PC before formatting or flashing. This is boring until it saves you.
Use a branded replacement card
Do not build your perfect setup on the no-name card that arrived in the box.
Follow the official guide
Use the project’s own docs or well-known community guides. Avoid random “all-in-one” packs from mystery download sites.
Test saves before filling the card
Install firmware, add one GBA game, save, reboot, load, and only then move your full library over.
Firmware picks by player type
I just want Pokémon hacks
Miyoo Mini Plus with OnionOS, or RG35XX Plus with muOS. Keep it simple and stable.
I want lots of systems
RG35XX H/Plus with KNULLI or muOS, or an R36S-style device with a well-supported ArkOS build.
I hate fiddling
Use OnionOS on Miyoo, or MinUI where supported. Less tinkering, more playing.
Firmware FAQ
Can custom firmware brick my handheld?
Usually you are just writing to the SD card, not permanently changing the device. Still, follow the correct guide for your exact model and keep the original card backed up.
Is OnionOS better than stock?
For Miyoo Mini Plus, yes for most users. It is cleaner, more polished and has better day-to-day features.
Which is better: muOS or KNULLI?
muOS is better if you want fast and simple. KNULLI is better if you like a richer frontend and do not mind more setup.
Should I delete the original card?
No. Back it up and keep it somewhere safe. It can help if you need original files or want to return the device to stock.