HTML5 game publishing
Optimizing HTML5 Game Load Time for Portal Submissions
A prioritized load-time checklist covering build size, compression, initial asset requests, fonts, audio, caching, and first interaction.
Measure the time from opening the game page to the first controllable frame. A canvas appearing is not enough if the player still waits for assets or initialization. Test a cold load with the browser cache cleared and a second load with cached assets, then keep both measurements with the build record.
Texture and image size, first
Sort the build output by file size before changing code. Oversized sprites and textures are easy to spot there. Export them near the largest displayed size, compare WebP and PNG quality where transparency permits, and verify texture-atlas dimensions against the target devices. Record the package size before and after each batch so you know which change helped.
Audio compression
Uncompressed WAV files add up fast. Compressed formats (OGG/MP3, or your engine's equivalent) at a reasonable bitrate are audibly fine for game SFX and music and are a fraction of the size — this is often the second-biggest easy win after images.
Loading strategy
- Load only what the first screen needs, then stream the rest in the background — don't block the title screen on assets for level 10.
- Show real loading feedback (a progress bar tied to actual bytes loaded), not a spinner — players tolerate a wait they can see the end of far better than an indefinite one.
- Cut splash screens and forced intro animations that add seconds before the player has any control — on a portal, that time is competing with the back button.
Engine-specific notes
Unity WebGL builds carry engine/runtime overhead on top of your actual content, which is why they tend to load slower than Construct, GDevelop, or Phaser games of similar scope — enabling Brotli/gzip compression on your build output and trimming unused engine modules (physics, XR support, etc.) helps but won't fully close that gap. For Godot exports, keep an eye on texture import settings specifically — the default import quality is tuned for desktop, not a web-optimized build.
A rough target
Do not publish a universal target based on your own connection. Choose representative desktop and mobile test conditions, record time to first input, and use the same conditions for every build. Check PlayKovo's current package limits in the submission rules before submitting.