OpenGL ES render-to-texture content is stored top-down

What changed?

Impeller's OpenGL ES backend now stores render-to-texture content top-down, the same as the Metal and Vulkan backends. A fragment shader or Flutter GPU app that sampled a render-target texture on OpenGL ES and added a vertical flip to compensate for the old bottom-up orientation now renders that content upside down.

Will this affect my application?

Who is affected: Applications and packages relying on the previous behaviour or signature. Code that uses FragmentShader.
Practical impact: Behaviour or API differences that can break builds or change runtime behaviour.
What action should I take?: Follow the official migration guide below, update affected call sites, run `dart fix --apply` where a fix is available, then run your tests.

APIs mentioned:FragmentShader

How do I migrate safely?

Before and after (from the official guide)

dart+0−3

Before

1		void main() {
2		vec2 uv = FlutterFragCoord().xy / u_size;
3	−	#ifdef IMPELLER_TARGET_OPENGLES
4	−	uv.y = 1.0 - uv.y;
5	−	#endif
6		fragColor = texture(u_texture, uv);
7		}

After

1		void main() {
2		vec2 uv = FlutterFragCoord().xy / u_size;



3		fragColor = texture(u_texture, uv);
4		}

Raw before / after

void main() {
  vec2 uv = FlutterFragCoord().xy / u_size;
#ifdef IMPELLER_TARGET_OPENGLES
  uv.y = 1.0 - uv.y;
#endif
  fragColor = texture(u_texture, uv);
}

void main() {
  vec2 uv = FlutterFragCoord().xy / u_size;
  fragColor = texture(u_texture, uv);
}

Official migration guide (excerpt, © The Flutter Authors, CC BY 3.0)

Shaders written for OpenGL ES often flipped the Y coordinate inside an IMPELLER_TARGET_OPENGLES block to make render-target textures match the other backends. Render-target textures are now top-down on every backend, so that flip is no longer needed.

Code before migration:

void main() {
  vec2 uv = FlutterFragCoord().xy / u_size;
#ifdef IMPELLER_TARGET_OPENGLES
  uv.y = 1.0 - uv.y;
#endif
  fragColor = texture(u_texture, uv);
}

If the shader only needs to run on a Flutter release that includes this change, remove the flip.

Code after migration:

void main() {
  vec2 uv = FlutterFragCoord().xy / u_size;
  fragColor = texture(u_texture, uv);
}

To keep one source working across releases, guard the flip with the IMPELLER_OPENGLES_UNFLIPPED_DEPRECATED macro. That macro is only defined on releases that store render-target textures top-down, so the flip still runs on older releases that need it.

void main() {
  vec2 uv = FlutterFragCoord().xy / u_size;
#if defined(IMPELLER_TARGET_OPENGLES) &#x26;&#x26; !defined(IMPELLER_OPENGLES_UNFLIPPED_DEPRECATED)
  uv.y = 1.0 - uv.y;
#endif
  fragColor = texture(u_texture, uv);
}

Migration assistantAI-generated · grounded in cited sources

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Evidence & verification

Official migration guide·Verified classification (95%)

Listed in the official breaking-changes index (docs.flutter.dev/release/breaking-changes).

An official announcement or migration guide documents an intended behaviour or API change. A verified source change (git diff) shows code changed but does not by itself prove a public API is breaking. AI interpretations are labelled and never used to classify a change.

Validation warnings

api-symbols: {"unresolved":["FragmentShader"]}

Source commit: b3045439b7c0
Source last updated: Oct 21, 2026
Last synchronized: Oct 21, 2026
Publication status: published

Publication history

Oct 21, 2026, 8:31 PM: new → published (ingestion) — Backed by an official breaking-change/migration guide.

AI explanationAI-generated · grounded in cited sources