WebAPI

Comprehensive Go WebAssembly (WASM) bindings for standard browser Web APIs (DOM, HTML, CSS, Fetch, WebGL, WebGPU, WebNN, WebCodecs, etc.).

Rather than handwriting thousands of bindings, webapi automatically generates idiomatic, type-safe Go bindings from official WebIDL specifications using webidl-bind.

[!Note] 🚧 Experimental 🚧: The project rework is relatively new, so there may still be breaking API updates — we will try to keep those as few and harmless as possible, and tag the versions appropriately.

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Features

• Standard Compliant: Generated directly from official W3C and WHATWG WebIDL specifications.
• Dual-File Compilation:
  • *_js.go: Native browser execution under GOOS=js GOARCH=wasm using syscall/js.
  • *.go: Host stub implementations under //go:build !js using core/js, enabling standard host toolchains, IDEs (gopls), linters, and go test to navigate and typecheck without switching environments.
• High-Throughput Buffer Conversions: Optimized array buffer copying between Go and JavaScript in core/jsconv (ToJS, FromJS, CopyToJS, CopyFromJS).
• Comprehensive API Coverage: Includes modern browser standards such as WebGPU, WebNN, WebCodecs, Cookie Store, File System Access, Storage Buckets, View Transitions, and Anchor Positioning.

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Installation

go get github.com/gowebapi/webapi

Requires Go 1.22+.

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Example: Button Counter

The following example binds to a DOM button element, sets its text, and increments a counter each time the button is clicked:

package main

import (
	"fmt"

	"github.com/gowebapi/webapi"
	"github.com/gowebapi/webapi/html"
	"github.com/gowebapi/webapi/html/htmlevent"
)

func main() {
	// Get the element from the DOM
	element := webapi.GetWindow().Document().GetElementById("myButton")

	// Cast it into the correct HTML element class
	button := html.HTMLButtonElementFromJS(element.JSValue())

	// Change text
	button.SetInnerText("Press me!")

	// Register an event callback that displays a click counter
	count := 1
	button.SetOnClick(func(event *htmlevent.MouseEvent, currentTarget *html.HTMLElement) {
		button.SetInnerText(fmt.Sprint("Count: ", count))
		count++
	})

	// Prevent program from terminating
	c := make(chan struct{}, 0)
	<-c
}

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Building and Running

1. Compile to WebAssembly

GOOS=js GOARCH=wasm go build -o main.wasm main.go

2. Run in the Browser

Serve main.wasm alongside Go's WebAssembly support file (wasm_exec.js) and an HTML loader:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <script src="wasm_exec.js"></script>
    <script>
        const go = new Go();
        WebAssembly.instantiateStreaming(fetch("main.wasm"), go.importObject).then((result) => {
            go.run(result.instance);
        });
    </script>
</head>
<body>
    <button id="myButton">Loading...</button>
</body>
</html>

(You can copy wasm_exec.js from your Go installation via cp $(go env GOROOT)/misc/wasm/wasm_exec.js . or $(go env GOROOT)/lib/wasm/wasm_exec.js depending on your Go version).

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Testing

• Host Stub Verification:

  go test ./...
  

• In-Browser WebAssembly Tests (using wasmbrowsertest):

  env -i PATH="$PATH" HOME="$HOME" DISPLAY="${DISPLAY:-:0}" \
    GOOS=js GOARCH=wasm go test -v \
    -exec="wasmbrowsertest" github.com/gowebapi/webapi/dom
  

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Package Overview

Domain	Key Packages	Description
Root & Core	webapi, core	Global scope accessors (GetWindow(), GetDocument()), JS interop wrappers
DOM	dom, dom/domcore, dom/geometry, dom/eyedropper	Nodes, Elements, Events, Mutation Observers, Geometry
HTML	html, html/canvas, html/media, html/worker	HTML elements, Canvas 2D, Audio/Video, Web Workers
CSS	css, css/cssom, css/viewtransitions, css/anchorposition	CSSOM, Animations, View Transitions, Anchor Positioning
Graphics & ML	graphics/webgl, graphics/webgpu, ml/webnn	WebGL 1 & 2, WebGPU, Web Neural Network API
Media	media/audio, media/webrtc, media/webcodecs	Web Audio, WebRTC, WebCodecs audio/video encoding & decoding
Storage & File	storage, cookie, file/fs, storage/buckets, storage/weblocks	Cookie Store, File System Access, Storage Buckets, Web Locks
Device & Hardware	device/serial, device/battery, device/computepressure, device/gamepad	Web Serial, Compute Pressure, Gamepad, Sensor APIs

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Changelog

• 2026/10/08: Modernized Go; Updated with recent APIs (Cookie Store, WebNN, etc.).