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The Javascript sizecoding community has been quite active for years now.

Setting up


Video display

There are basically a ways to go about getting some graphics on screen: Minimal 2D Canvas, WebGL and WebAssembly.

Minimal 2D Canvas

Here a a couple of minimal HTML 2D Canvas setups for animation:

<canvas id=c style=width:99%><svg onload=setInterval('',t=9)>
<canvas id=c style=width:99% onclick=setInterval('',t=9)>
<canvas id=c><svg onload=setInterval('',t=9)>
<canvas id=c onclick=setInterval('',t=9)>
<svg onload=setInterval('',t=9)>

And here are a few for static content:

<canvas id=c><svg onload=''>
<svg onload=''>

A minimal 2D Canvas Example

Here would be an example of a simple 128 byte setup of a scrolling XOR-pattern using grayscale.

<canvas id=c onclick=setInterval('for(c.width=w=320,++t,o=w*w;o--;c.getContext`2d`.fillRect(X=o%w,Y=o/w,1-(X+t^Y)/99,1));',t=9)>

And here is one for static text content in 64 bytes.

<svg onload=for(i=8160;i--;)write(i%128?i/128&i?'_':'#':'\n')>


To be added.

Dwitter template

This is a dwitter template that will allow you to directly convert a dweet to a working standalone javascript/html

<body><canvas id=c width=1920 height=1080 style=width:100%>
u=t=>{// dweet code goes heres}


It is also possible to bootstrap a base64 binary of WebAssembly directly into HTML. There is a toolchain called wasmer ( ) that helps you do this. Now you can write WASM code that writes pixeldata to memory and bootstrap that to HTML.


Here are a few methods to get sound for your tiny intro. Note that all of these methods will need a user-click to active the browser and start the intro.

Audio Buffer Source

// Audio element + Wave PCM
for(t=0;t++<8e5;) d+=String.fromCharCode(/*ByteBeat*/);
Z=new Audio(h+btoa(d));;

Audio Buffer Source

// Audio element + buffer
A=new AudioContext;B=A.createBuffer(1, 8e5, freq);d=B.getChannelData(0);
for(t=0;t<8e5;t++) d[t]= /* FloatBeat */;

Other Methods

Audio worklets, Nodes, WebGL, Speechsynth

More information


When it comes to compressing your code, there are several options you can consider:

RegPack / jscrush

The default packesr that helps to rename and shuffle variables and code contructs to pack Javascript code. No additional bootstrapping overhead needed.

JSCrush works by:

  • Finding the first unused ASCII character to act as the join
  • Finding the substring of the program text that gives the best space savings if its repetitions are all replaced by the ASCII character from 1.
  • Splitting the source on 2 and joining the pieces using 1, tacking on 2 to the end. This string replaces the original source.
  • Repeating 1, 2 and 3 until no more savings are possible or we’re all out of ASCII.
  • Wrapping the compressed source into a string, then using the list of join ASCII characters to unroll the string.
  • Unrolling is performed by splitting on every ASCII character used in 3, extracting the original repeated substring 2 from the split and joining the parts.

Using DecompressionStream

On modern browsers its possible to use HTML self decompression based on the DecompressionStream API

Bootstrapping PNG

It is possible to bootstrap ZLIB compressed code by encoding your code inside a (usually single line) PNG file and bootstrap that from HTML. For example the pnginator tool helps you create such a PNG file. Overhead size for bootstrapping the PNG is about 160 bytes so it is mostly viable for 1K and bigger sized intros.

Bootstrapping WEBP

The same technique is also possible for WEBP files, which use a LZ type of compression which tends to work a little less efficient. on compressing code.

Bootstrapping Brotli

It is also possible to bootstap Brotli compressed code to a WOFF2 font as described here:

Which can then be bootsrapped using the tool above and accessed from HTML with the following (256 character) code:

<body[ARBITRARY_BYTES_HERE] onload="new FontFace('x','url(#').load(C=$.getContext`2d`).then(A=>{document.fonts.add(A);C.font='1pc x';K=String.fromCharCode;for(A=I='';I<[NUM_GLYPHS];A+=K(W>>8,W&255))W=C.measureText(K(2e4+I++)).width;eval(A)})"><canvas id=$>

Or alternatively, if you are lucky maybe some parties will accept brotli code directly when you provide your own server:

require("http").createServer((req, res) => {
  const path = (req.url || "/").slice(1);
  if (path === "") {
    const buffer = require("fs").readFileSync("");
    res.setHeader("Content-Type", "text/html");
    res.setHeader("Content-Encoding", "br");
    res.setHeader("Content-Length", buffer.byteLength);
Open http://localhost:1337 to watch intro.
This mini http server is only here to pass the Content-Encoding we are missing on file:// compared to the normal environment of a web page

Additional Resources


Tutorials / Postmortems


Browser Intros

Other Links