nesflix-web

In-browser port of NESFlix (2011) by NO CARRIER and Batsly Adams. The output is a playable NES ROM that you can run on any MMC3-capable cartridge, flash cart (PowerPak, Everdrive N8), or emulator.

The original tool utilizes a Java app that has become increasingly hard to run on modern systems. This is a re-implementation in JavaScript that runs entirely in a browser.

https://k6lcm.github.io/nesflix-web/

• NESFlix (the NES engine and assembly source) by NO CARRIER, 2011. https://no-carrier.com · https://github.com/no-carrier/NESFlix
• NESFlixTool (the conversion algorithm) by Batsly Adams.
• Web port by Levi C. Maaia (2026). https://www.youtube.com/@levimaaia
• Distributed under GPL v3 or later, matching the original. See LICENSE.

1. Prep your GIF following Batsly Adams' original Photoshop tutorial or Levi's Digital Voyage video tutorial using Ezgif.com (just come back here before venturing off into the original NESFlix Java app): loop trim, resize to 128×128, reduce to 4 colors, uncheck transparency, save as GIF. The file must end up exactly 128×128 with no more than 64 frames and exactly 4 distinct colors.
2. Go to https://k6lcm.github.io/nesflix-web/.
3. Choose your GIF. Optionally tick "delete first tile" if your video should sit inside a solid border (this matches the original tool's checkbox).
4. Click convert then download. A .nes file downloads.
5. Play it on hardware (PowerPak, Everdrive N8, ReproPak) or in an emulator (Nestopia, FCEUX, Mesen).

Controller mapping is the same as the original NESFlix ROM. See the original readme.txt in NO CARRIER's repo for the full controls list.

In scope:

• MMC3 path, up to 64 frames
• Optional "delete first tile" behavior, identical to the original
• The same validation errors the original tool reports
• Separate PRG.bin and CHR.bin files availavble for burning physical EPROMs. The PRG download has the 16-byte iNES header stripped. Note: I have not yet burned these to a physical EPROM and booted on hardware. If you try it on a real cart, let me know how it goes.

Out of scope (for now):

• MMC5 path (up to 256 frames). Different .asm, different banking. Can be added later; not required for the common case.
• AUTOCONVERT. The experimental "feed it any GIF and we'll grayscale- and-posterize it" mode. Batsly Adams himself documented it as "works on some GIFs." If you want reliable results, do the Photoshop prep.

This is a port, not a fix. Behavior is intentionally bug-for-bug compatible with NESFlixTool. Two things to be aware of:

1. Per-frame palette sort. The original tool scans each frame independently for its distinct colors and sorts them by ARGB integer value. The pixel value 0 to 3 in the resulting CHR is the color's rank in that sorted list. For grayscale content this is darkest-to-lightest. For color content it's R, then G, then B order. The engine then maps values 0 to 3 through one of 8 NES palettes (default is black / dark gray / light gray / white).
2. Non-cleared color array. The 4-slot palette array is not reset between frames. If a frame uses fewer than 4 of the GIF's distinct colors, stale entries from a prior frame remain in the array and get sorted in. On unusual GIFs this can show up as one or two frames with their colors rearranged mid-playback. Properly-prepped GIFs where every frame uses all 4 palette colors are unaffected. NO CARRIER's distributed adorn.gif is one such GIF, which is why our test.html passes byte-exact on it.

A future version may offer an opt-in "global palette" mode that fixes quirk 2. v1 does not, on purpose.

Clone the repo and serve it with any small HTTP server. The browser won't load the bundled assets/ and test/ files from a file:// URL because of the same-origin policy, so a server is required even for read-only inspection.

git clone https://github.com/k6lcm/nesflix-web
cd nesflix-web
python3 -m http.server 8000

Then open http://localhost:8000/ for the converter, or http://localhost:8000/test/test.html for the fidelity test.

The fidelity test runs the in-browser converter on the adorn.gif that ships with NO CARRIER's original distribution and compares the resulting CHR-ROM byte for byte against the canonical mmc3.chr from that same distribution. A pass means the JavaScript port produces bit-identical output to the 2011 Java tool on the same input.

Expected SHA-256 of the CHR section: c698380daa7a7677c55c75542ef60ca2e42276337486c7c9967b770880b320e0

Expected SHA-256 of the full .nes produced from adorn.gif: ecf177f84db8a76e3768341e3e5ed202ccdf87d472332e0e52ab8b8319b842cf

nesflix-web/
  index.html               main UI
  app.js                   UI glue
  converter.js             the algorithm (~280 lines, commented)
  style.css
  assets/
    template.bin           assembled PRG from nesflix_mmc3.asm (32,784 bytes)
    adorn.gif              NO CARRIER's sample input
  vendor/
    gifuct.js              vendored gifuct-js, MIT, ~7.5 KB
  test/
    test.html              byte-identity fidelity test
    adorn_reference.chr    NO CARRIER's mmc3.chr, the canonical output
  LICENSE                  GPL v3
  README.md

assets/template.bin is the assembled output of asm6 nesflix_mmc3.asm from NO CARRIER's repo. It is a static asset baked into the project. To reproduce it from source:

git clone https://github.com/no-carrier/NESFlix
cd NESFlix
asm6 nesflix_mmc3.asm template.bin

The result should be exactly 32,784 bytes with SHA-256 42db193dec37efcb606faa770001323bf57c367a93622ec421e663e7eed058a0.

(asm6 by loopy is available from a few public mirrors; asm6f is a backwards-compatible fork that produces identical output for this .asm.)