---
title: "WebGL2 backend: API"
package: "@phaser-ae/render-webgl2"
tier: Free
version: 3.0.0-8
released: 2026-10-14
updated: 2026-10-20
description: "The WebGL2 half of the renderer, drawing the same worlds and game calls as WebGPU so a game also runs on devices without it."
url: https://phaser.io/packs/render-webgl2/api
site: Phaser - https://phaser.io
---

# WebGL2 backend: API

`@phaser-ae/render-webgl2` — The WebGL2 backend render-auto falls back to on devices without WebGPU. Compose render-auto unless a test or build needs WebGL2 alone.

## The pack

### `webgl2`

```ts
function webgl2(): Pack<{ gl: WebGl2Api; preloader: PreloaderApi }>
```

The WebGL2 backend pack. Draws the worlds' sorted sprite tables from the kernel atlas, and each big picture from
its texture of its own — world-space in `sprites` (with world-screen's underlay among them), screen-space in
`screen` — with the same instance layout, the
same run splitting and the same blend table as `render-webgpu`. Compose it INSTEAD of `render-webgpu`, never
beside it. Headless it attaches and draws nothing.

## Functions

### `blendTable`

```ts
function blendTable(gl: WebGL2RenderingContext): GlBlend[]
```

Build the table from a live context's enum values, so nothing here hard-codes a GL constant.

### `fragmentGLSL`

```ts
function fragmentGLSL(customs:ReadonlyArray<{id:number;def:DeformDef}>,blocky:boolean):string
```

Custom fragment snippets share the same straight-alpha working colour as WebGPU.

### `installWebGl2`

```ts
function installWebGl2(k: Kernel, deferRegistration = false): { gl: WebGl2Api; initialise(): void; register(): void }
```

Install one backend's passes and commands; the caller controls device initialisation.

## Constants

### `FRAG`

```ts
const FRAG: "#version 300 es\nprecision highp float;\nconst bool BLOCKY = false;\nuniform sampler2D uTex;\nin vec2 vUvn;\nin vec4 vTint;\nin vec4 vUv;\nin vec4 vTile;\nin float vShade;\nin vec3 vMeta;\nflat in float vCutoff;\nout vec4 outColor;\nvoid main() {\n // tiling: wrap inside the frame's atlas rect, so a 4×1 repeat d... …
```

The fragment stage: the frame's rect (in the atlas, or in a picture's own texture), tiled, tinted, premultiplied out.

### `VERT`

```ts
const VERT = (gridX: number, gridY = gridX, customs: ReadonlyArray<{id:number;def:DeformDef}> = [])=> …
```

The vertex stage: one instanced quad, or a rectangular grid when a deformer is on.

## Types

### `GlBlend`

```ts
interface GlBlend
```

The blend table, in the same order as the backend's: normal, add, multiply, screen, subtract.

Premultiplied source throughout — the atlas and the tint both carry their alpha — so every mode is a pair
of factors and an equation, exactly as it is on the WebGPU side.

- `srcRGB: number` — GL blend factor (an enum value such as `gl.ONE`) applied to the source colour channels.
- `dstRGB: number` — GL blend factor applied to the destination colour channels.
- `srcA: number` — GL blend factor applied to the source alpha.
- `dstA: number` — GL blend factor applied to the destination alpha.
- `eq: number` — GL blend equation enum (`gl.FUNC_ADD` or `gl.FUNC_REVERSE_SUBTRACT`) that combines the two terms.

### `WebGl2Api`

```ts
interface WebGl2Api
```

`game.gl`.

- `readonly ready: boolean` — True once the context and the program are live.
- `readonly drawCalls: number` — Draw calls in the last frame.
- `readonly instances: number` — Instances in the last frame.
- `readonly missing: ReadonlyArray<string>` — The registered DRAWERS this backend cannot run — a pack asked for its own pipeline and got nothing. A game that wants to warn the player, or hide a feature, reads this rather than guessing.

---

## For AI agents: Phaser AE

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- **Phaser AE in the browser** (https://phaser.io/agent): the game's design, and a crew of bots that make its art, sprites, music, sound effects, logos, title screens, game UI, textures, shaders, 3D models and video, then build, test and publish the game. Every tool there is registered with Web MCP (`document.modelContext`, with `window.phaserDesk` for browsers without it), so an agent in the user's browser can call the tools directly once the user is signed in. Tools that make something spend the user's credits.
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Read any page of this site as Markdown by adding `.md` to its URL (the home page is https://phaser.io/index.md), or by asking for `text/markdown`. The index for agents is https://phaser.io/llms.txt. On the site's pages, the browser's Web MCP also offers `phaser_ae_guide`, `read_page_as_markdown` and `open_phaser_ae`.