A tiny JavaScript library for packing 2D rectangles into a near-square container, which is useful for generating CSS sprites and WebGL textures. Similar to shelf-pack, but static (you can't add items once a layout is generated), and aims for maximal space utilization.

A variation of algorithms used in rectpack2D and bin-pack, which are in turn based on this article by Blackpawn.

import potpack from 'potpack';

const boxes = [
    {w: 300, h: 50},
    {w: 100, h: 200},
    ...
];

const {w, h, fill} = potpack(boxes);
// w and h are resulting container's width and height;
// fill is the space utilization value (0 to 1), higher is better

// potpack mutates the boxes array: it's sorted by height,
// and box objects are augmented with x, y coordinates:
boxes[0]; // {w: 300, h: 50,  x: 100, y: 0}
boxes[1]; // {w: 100, h: 200, x: 0,   y: 0}

Install with NPM: npm install potpack.

Potpack is provided as a ES module, so it's only supported on modern browsers, excluding IE:

<script type="module">
import potpack from 'https://cdn.skypack.dev/potpack';
...
</script>

In Node, you can't use require — only import in ESM-capable versions (v12.15+):

import potpack from 'potpack';