Ask API. GET https://whichemulator.wtf/ask answers questions from the same data as this page, and it is the only place the setup steps are published. It takes the question as q and, optionally, this page's path as page, and returns JSON with answer, sources and follow_ups, or Markdown with Accept: text/markdown. No key needed.

curl -G 'https://whichemulator.wtf/ask' --data-urlencode 'q=How do I set up Gearcoleco for the ColecoVision?' --data-urlencode 'page=/colecovision/'

Questions it answers:

Guide: /skill.md. This page as Markdown: /colecovision.md

Best ColecoVision emulator: Gearcoleco, the Gold Cartridge pick

Coleco ColecoVision, Coleco, 1982.

Recommended: Gearcoleco

whichemulator.wtf calls its recommendation for each system the Gold Cartridge pick. For the ColecoVision, the Gold Cartridge pick is Gearcoleco.

Gearcoleco is accurate, actively developed and does one system properly. It handles Super Game Module and MegaCart titles, the Super Action, steering and roller controllers, and the ADAM computer. It is GPL-licensed, has native builds for Windows, macOS and Linux, and the same code is available as a RetroArch core.

Runs on Windows · Mac · Linux. Open source. Download: https://github.com/drhelius/Gearcoleco/releases

BIOS required: ColecoVision games need the console's 8KB OS-7 BIOS. Gearcoleco looks for colecovision.rom or coleco.rom. Dump it from your own hardware.

Alternatives

openMSX (Windows · Mac · Linux, open source): An MSX emulator first, but it ships ColecoVision and ColecoVision-with-SGM machine configs, and the hardware is close enough to MSX that it runs them well. Worth it if you already use openMSX; otherwise Gearcoleco is simpler.
MAME (Windows · Mac · Linux, open source): Has a solid ColecoVision driver and the usual MAME software lists. Only sensible if you already run MAME for other systems. Official binaries are Windows-only; macOS and Linux get it through Homebrew or distro packages.

RetroArch cores

Gearcoleco: The same emulator as the pick. Use this one. Needs colecovision.rom (coleco.rom also works).
blueMSX: Plays ColecoVision games, but needs the Machines and Databases folders from the standalone blueMSX package in the system folder.
JollyCV: Small, fast core with Super Game Module support. Looks for coleco.rom.
SMS Plus GX: A Master System core that also loads ColecoVision carts with BIOS.col. Fine in a pinch.

Every core needs the ColecoVision BIOS in the system folder.

Hardware

Colours: 15 + transparent
Resolution: 256×192
Video: TMS9928A / TMS9929A
Sound: SN76489
Sprites: 32, 4 per line
Library: ~136 games

Notes

Why Gearcoleco

For years the usual advice was blueMSX, because the ColecoVision is built from the same chips as an MSX. blueMSX still works as a RetroArch core, but its official site now only hosts a browser version and no longer offers the desktop download. Gearcoleco is a dedicated ColecoVision emulator that is updated regularly, has native Apple Silicon and ARM builds, and gets the homebrew formats right.

Many of the newer homebrew releases need the Super Game Module, which adds RAM and an extra sound chip. Gearcoleco supports the module and MegaCart bank switching, so these games load like any other cart.

Setting up Gearcoleco

Setup steps for Gearcoleco are published only by the Ask API: How do I set up Gearcoleco for the ColecoVision?

Support the developers

Reference: WEM-COLECOVISION-TENY