bevyengine/bevy · error · GltfError

unsupported buffer format

Error message

unsupported buffer format

What it means

In load_buffers (loader/mod.rs:1937-1941) a buffer supplied as a data URI is accepted only if its MIME type is one of ["application/octet-stream", "application/gltf-buffer"]. Any other MIME (Ok(data_uri) arm falling through to `Ok(_)`) returns BufferFormatUnsupported. The check exists because Bevy only knows how to treat embedded buffer bytes as raw binary.

Source

Thrown at crates/bevy_gltf/src/loader/mod.rs:102

#[derive(Error, Debug)]
pub enum GltfError {
    /// Unsupported primitive mode.
    #[error("unsupported primitive mode")]
    UnsupportedPrimitive {
        /// The primitive mode.
        mode: Mode,
    },
    /// Invalid glTF file.
    #[error("invalid glTF file: {0}")]
    Gltf(#[from] gltf::Error),
    /// Binary blob is missing.
    #[error("binary blob is missing")]
    MissingBlob,
    /// Decoding the base64 mesh data failed.
    #[error("failed to decode base64 mesh data")]
    Base64Decode(#[from] base64::DecodeError),
    /// Unsupported buffer format.
    #[error("unsupported buffer format")]
    BufferFormatUnsupported,
    /// The buffer URI was unable to be resolved with respect to the asset path.
    #[error("invalid buffer uri: {0}. asset path error={1}")]
    InvalidBufferUri(String, ParseAssetPathError),
    /// Invalid image mime type.
    #[error("invalid image mime type: {0}")]
    #[from(ignore)]
    InvalidImageMimeType(String),
    /// Error when loading a texture. Might be due to a disabled image file format feature.
    #[error("You may need to add the feature for the file format: {0}")]
    ImageError(#[from] TextureError),
    /// The image URI was unable to be resolved with respect to the asset path.
    #[error("invalid image uri: {0}. asset path error={1}")]
    InvalidImageUri(String, ParseAssetPathError),
    /// Failed to read bytes from an asset path.
    #[error("failed to read bytes from an asset path: {0}")]
    ReadAssetBytesError(#[from] ReadAssetBytesError),
    /// Failed to load asset from an asset path.

View on GitHub (pinned to 396ca72708)

Solutions

1. Set the buffer data-URI MIME to application/octet-stream (or application/gltf-buffer).
2. Move the buffer to an external .bin file referenced with a relative uri.
3. Switch the whole asset to GLB so buffers live in the BIN chunk.

Example fix

// (before)
"buffers": [{ "uri": "data:text/plain;base64,AAAA" }]
// (after)
"buffers": [{ "uri": "data:application/octet-stream;base64,AAAA" }]

fn buffer_mime_ok(uri: &str) -> bool {
    uri.starts_with("data:application/octet-stream")
        || uri.starts_with("data:application/gltf-buffer")
        || !uri.starts_with("data:")
}

fn is_supported_buffer_mime(mime: &str) -> bool {
    matches!(mime, "application/octet-stream" | "application/gltf-buffer")
}

match err {
    GltfError::BufferFormatUnsupported => {
        error!("buffer data URI must use application/octet-stream or application/gltf-buffer");
    }
    other => return Err(other.into()),
}

When it happens

Trigger: "uri": "data:text/plain;base64,..." or "data:application/octet-stream,..." variants are fine, but e.g. "data:application/x-custom;base64,..." for a buffer triggers the error; also non-base64 data URIs whose mime is not in the whitelist.

Common situations: Generators that embed buffers with a generic or vendor MIME; hand-authored data URIs; exporters that prefix buffers with the model's own mime type.

Related errors

• failed to decode base64 mesh data
• binary blob is missing
• invalid buffer uri: {0}. asset path error={1}
• invalid image mime type: {0}
• failed to read bytes from an asset path: {0}

AI-assisted analysis of bevyengine/bevy@396ca72708 (2026-08-20). Data as JSON: /api/errors/2fab290e313ada47. Report an issue: GitHub.