Download size is the compressed bytes the browser fetches over the network before your game starts; GPU VRAM is the uncompressed memory textures, meshes and buffers occupy on the graphics card once decoded. A small download can still blow the VRAM budget on low-end devices.
At a glance
| Fact | Value | Source |
|---|---|---|
| KTX reduces both file size and GPU memory | container format | khronos.org |
| gltfpack compresses glTF for smaller downloads | meshoptimizer codecs | github.com |
Download size is what the browser transfers over the network before the game can start: compressed textures, audio, meshes, JavaScript and your engine’s WebGL runtime, all measured in the bytes a CDN or portal serves. GPU VRAM is different: it’s the memory a texture or mesh occupies on the graphics card after it’s decoded and uploaded, which is almost always much larger than the compressed file. A 2 MB JPEG can decode into tens of megabytes of raw pixel data sitting in VRAM, and that memory is shared with whatever else is open in the browser tab.
If you’re building the game with an AI coding agent, Playgama MCP lets that agent upload builds, covers and leaderboard data straight from Claude Code, Cursor or VS Code and get a QA Tool link to test the result, without leaving the IDE.
When preparing games for web portals, the download budget and the VRAM budget need separate tracking. Cutting download size with aggressive JPEG or PNG compression does nothing for VRAM if the decoded resolution stays the same.
How to manage both
- Use glTF with KTX textures: KTX is a container built to reduce both file size and GPU memory usage, unlike JPEG/PNG which only shrink the download.
- Run models through gltfpack to cut download size further with meshoptimizer codecs, separate from any texture compression.
- Cap texture resolution and mesh detail per device tier – VRAM limits vary far more across phones than download bandwidth does.
- Test on low-end Android and older iOS Safari, where WebGL VRAM ceilings are tightest.
Sources
- glTF – Runtime 3D Asset Delivery
- Developer Docs โ OnlineGameWorlds
- gltfpack / meshoptimizer README
- MDN: WebGL API
Related questions
Does a smaller download always mean less GPU memory use?
No. Download size reflects compressed bytes; VRAM reflects decoded texture and mesh data. A heavily compressed texture can still decode to a large uncompressed size in VRAM.
Can KTX textures help with WebGL performance directly?
Yes, KTX is designed to reduce both download size and GPU memory usage, unlike standard JPEG or PNG which only reduce the transferred file size.
Last updated: 30 September 2026