WebLib — HTML/CSS/JS GUIs for Minecraft NeoForge 1.21

WebLib (web_lib) is a lightweight library mod that lets mod developers build fully-featured Minecraft GUI screens using standard HTML and CSS, with a simple JavaScript-to-Java callback bridge — all rendered natively via Minecraft's own GuiGraphics, with zero external browser dependencies.

Stop wrestling with Minecraft's widget system. Write your mod's menus the way web developers write interfaces.

Features

HTML rendering — Supports a rich set of elements: div, p, h1–h6, span, button, input, select, img, ul/ol/li, pre, hr, code, and more.
Full CSS engine — Cascade, inheritance, specificity, and a broad property set including:
- Box model (margin, padding, border, width, height)
- Flexbox (flex-direction, justify-content, align-items, flex-wrap, gap)
- Colors (#RGB, #RRGGBB, #RRGGBBAA, rgb(), rgba(), named colors)
- Text styling, overflow, z-index, relative positioning, and more
- Selectors: type, class, ID, attribute, pseudo-classes (:hover, :active, :focus, :nth-child, :not, etc.), and all combinators
JavaScript bridge — Fire Java callbacks directly from HTML onclick/onchange events. Pass arguments, access and mutate the DOM from Java.
Built-in JS functions — alert(), navigate(), reload(), setStyle(), setInnerText(), toggleClass(), setVar(), console.log() — no registration needed.
Multi-page navigation — Build multi-screen UIs with back ◀ / forward ▶ / reload ↺ browser chrome, or go headless.
External CSS & JS files — Reference stylesheet and script files from your mod's assets using the standard namespace:path ResourceLocation convention.
Resource-based pages — Load HTML pages directly from your mod's resource pack with WebLibApi.openPageFromResource(...).
Advanced WebPage API — Build, inject CSS, mutate, and layout pages programmatically before opening them.

For Mod Developers

Adding WebLib to your mod is a single dependency declaration:

[[dependencies.yourmod]]
    modId = "web_lib"
    type = "required"
    versionRange = "[1.0,)"
    ordering = "AFTER"
    side = "CLIENT"

Then open any screen with a single call:

WebLibApi.openPage("<html><body><h1>Hello, Minecraft!</h1></body></html>");

WebLibApi.registerFunction("myMod.openShop", (args, ctx) -> {
    Minecraft.getInstance().tell(() -> Minecraft.getInstance().setScreen(new MyShopScreen()));
    return null;
});