The questions that come up before the fun does.
Condensed from melonDS's ownHowto/FAQ page, which has the full walkthrough of every setting if you need more than the short version.
Getting started
What files does melonDS need before it'll boot anything?
BIOS and firmware dumped from real hardware: a 4KB ARM9 BIOS, a 16KB ARM7 BIOS, and a firmware file (128/256/512KB depending on whether it came from a DSi/3DS, a regular DS, or an iQue DS). Set the paths under Emu Settings → DS-mode.
Why won't my firmware boot?
DSi/3DS-sourced DS-mode firmware isn't bootable on its own. Either supply a genuine DS or iQue DS firmware dump, or enable "Boot game directly" to skip the boot screen entirely.
What extra files does DSi emulation need?
A 64KB ARM9 BIOS, a 64KB ARM7 BIOS, a 128KB firmware, and a roughly 240MB NAND dump — all obtained from your own DSi via a separate dumper tool.
Where do I get ROMs?
Dump your own game carts using a DSi or 3DS system and copy the resulting files over. melonDS doesn't provide, host, or link to ROMs.
Playing
How do savestates work?
Shift+F1 through Shift+F9 saves to a slot, F1 through F9 loads it back, and F12 undoes the last load. Turn on "Separate savefiles" first if you want savestates to leave your original save data untouched.
Can I import a save file from another emulator?
Yes — as long as the save file's size matches exactly what melonDS expects for that game.
Multiplayer isn't working.
Wifi support is still a work in progress and not every game supports it. Local multiplayer can also be unstable; disabling the framerate limiter sometimes helps.
Development & support
Is there an official Android or mobile version?
No. Android and other mobile builds are unofficial third-party ports, and the melonDS team doesn't support them.
I found a bug, or I have a feature idea.
File it on the project's GitHub issue tracker, or bring it up on the forums — both are linked from the Community page.
Why name it melonDS?
Why not?