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c64js

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What c64js is

c64js is an early Commodore 64 emulator built in vanilla JavaScript, with a browser demo for trying C64 ROM files and games. To run a compatible program, drop a .prg file onto the emulator canvas. The maker describes the demo as a proof of concept, not a complete emulator: it does not emulate the SID sound chip, and some VIC-II graphical modes are missing. The project says that only a limited number of ROMs work and that others may not run flawlessly because parts of the original hardware are not implemented. Its demo suggests SoS’s Flappy Birds implementation as an example to try. c64js is free, with web and self-hosted availability, and its code is released under the MIT license. The repository also welcomes contributions and provides build instructions using npm packages and gulp.

Who it suits

c64js suits people who want to try C64 .prg files in a browser or explore a JavaScript emulator project. Its limitations matter for anyone expecting broad ROM compatibility, sound, or complete graphics support.

What it does well

  • Free to use.
  • Browser demo accepts .prg files on the canvas.
  • Available for web use or self-hosting.
  • Code is released under the MIT license.
  • Repository welcomes contributions.

What to know first

  • Proof of concept, not a fully working emulator.
  • SID sound is not emulated.
  • Some VIC-II graphical modes are missing.
  • Only a limited number of ROMs work.

Limits

The emulator does not yet emulate the SID sound chip and omits some VIC-II graphical modes. The maker says only a limited number of ROMs work and that some will not run flawlessly.

Getting started

  1. Open the c64js browser demo
  2. Prepare a C64 ROM in .prg format
  3. Drop the file onto the emulator canvas
  4. For self-hosting, install the npm packages
  5. Build the distribution with gulp

Verdict

c64js offers a free way to try some C64 programs in a browser. Its proof-of-concept status and missing hardware features limit compatibility and sound and graphics support.

Questions

Is c64js free?

Yes. c64js is free and has no separate free trial.

Which file format does it run?

The emulator accepts ROM files in .prg format.

Where can I use c64js?

It is available on the web and can also be self-hosted.

Does it emulate C64 sound?

No. The SID chip responsible for sound is not emulated yet.

What license does the project use?

The code is released under the MIT license.

Who made c64js?

The project identifies Mikael Borgbrant as its maker; his GitHub profile lists Stockholm, Sweden.

Facts from c64js's own pages

Build
The README says to install npm packages with npm install and build the distribution with gulp. · github.com, 10 Oct 2026
Compatibility
The project says not all ROMs execute flawlessly because not every feature of the original hardware is implemented. · mborgbrant.github.io, 10 Oct 2026
Contributions
The project welcomes contributions and links to contribution guidelines. · github.com, 10 Oct 2026
Demo
The project links to a browser demo hosted on GitHub Pages. · github.com, 10 Oct 2026
Emulation status
The project describes itself as a proof of concept rather than a fully working emulator. · mborgbrant.github.io, 10 Oct 2026
Example
The demo page recommends SoS's Flappy Birds implementation for trying a game in the emulator. · mborgbrant.github.io, 10 Oct 2026
Graphics limits
Some VIC-II graphical modes are not emulated, and only a limited number of ROMs work. · github.com, 10 Oct 2026
Graphics support
Some graphical modes in the VIC-II chip are not emulated, and the repository says the chip is not fully emulated. · mborgbrant.github.io, 9 Oct 2026
Implementation
The emulator is written in vanilla JavaScript. · github.com, 10 Oct 2026
Intended audience
The project presents an emulator demo for trying C64 ROMs and games in a browser. · mborgbrant.github.io, 9 Oct 2026
License
The code and documentation are released under the MIT license. · github.com, 10 Oct 2026
Maker
The project copyright and GitHub profile identify Mikael Borgbrant; the profile lists Stockholm, Sweden. · github.com, 9 Oct 2026
Proof of concept
The demo page says the emulator is a proof of concept rather than a fully working emulator. · mborgbrant.github.io, 9 Oct 2026
Purpose
c64js is an early Commodore 64 emulator written from scratch in JavaScript. · github.com, 10 Oct 2026
ROM compatibility
The maker says not all ROMs will run flawlessly because not every feature of the original hardware is implemented. · mborgbrant.github.io, 9 Oct 2026
ROM loading
Users can run ROM files in .prg format by dropping them on the emulator canvas. · github.com, 10 Oct 2026
Sound
The SID chip for sound is not emulated. · mborgbrant.github.io, 10 Oct 2026
Sound support
The SID chip, which handles sound, is not emulated yet. · mborgbrant.github.io, 9 Oct 2026

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