# Essential Formatting Guidelines for Itch.io HTML5 Web Game Exports
Publishing HTML5 and WebGL games on Itch.io requires precise configuration of viewport dimensions, archive file structures, and cross-origin security headers. Unlike desktop executable downloads, browser-based games must load seamlessly inside an embedded iframe container without generating unintended scrollbars, black letterbox borders, or canvas clipping across desktop monitors, laptops, and mobile screens. 16:9 Landscape Standard Web Aspect Ratio
960 x 540 px Classic Itch Resolution
index.html in Root Entry Point File Requirement
COOP / COEP Headers Godot 4 Requirement
# Comparing Engine Web Export Requirements across Frameworks
Different game engines produce unique web export bundles that dictate how assets and WebAssembly binaries interact with the browser context. Understanding engine-specific constraints helps developers eliminate load failures before making their game public.Godot Engine (HTML5 Export)
Generates index.html alongside WebAssembly (.wasm) and main data package (.pck) binaries. Godot 4 requires SharedArrayBuffer support enabled in Itch.io project settings for multi-threaded WebGL performance.
Unity WebGL Build
Structures builds inside a Build/ directory containing framework.js, data, and wasm files. Canvas size is fixed in unityFramework loader settings and requires explicit iframe sizing to prevent scrollbars.
Phaser & Construct Web Exports
Lightweight JavaScript builds utilizing HTML5 canvas or WebGL renderers. Ideal for responsive full-window scaling and low memory footprint on mobile browsers.
# Common Itch.io Packaging Errors and Resolution Best Practices
| Issue Type | Root Cause | Recommended Solution |
|---|---|---|
| Nested index.html | Zipping parent folder instead of contents | Ensure index.html is located directly in the root directory of the archive. |
| Case-sensitivity 404 | File paths matching lower/upper case mismatches | Keep all file extensions and asset references lowercase to prevent Linux server 404s. |
| Canvas Scrollbars | Viewport dimensions smaller than canvas size | Set Itch.io embed viewport dimensions 20px larger than canvas or disable canvas overflow margins. |
| Uncompressed Audio | Large WAV files included in web package | Compress sound effects and music tracks into OGG or MP3 formats to decrease initial download time. |
When embedding a 1280x720 WebGL game on Itch.io, set your embed viewport dimensions to exactly 1280x720 with "Embed in page" enabled and "Click to launch" disabled. Always test fullscreen mode toggles to ensure the canvas scales dynamically across display aspect ratios.