BerriAI/litellm · error · ValueError

Unsupported image type. Expected either image url or base64

Error message

Unsupported image type. Expected either image url or base64 encoded string

What it means

Thrown by BedrockImageProcessor.process_image_sync when converting an OpenAI-style image_url to a Bedrock image block. The dispatcher only recognizes two shapes: strings containing the literal substring 'base64' (data URIs) and strings containing 'http://' or 'https://'. Anything else (file paths, s3:// URLs, bare base64 without the 'base64' marker, gs:// URLs) falls through to this ValueError.

Source

Thrown at litellm/litellm_core_utils/prompt_templates/factory.py:3582

                    name=document_name,
                )
            )
        elif is_video:
            return BedrockContentBlock(video=BedrockVideoBlock(source=_blob, format=image_format))
        else:
            return BedrockContentBlock(image=BedrockImageBlock(source=_blob, format=image_format))

    @classmethod
    def process_image_sync(cls, image_url: str, format: str | None = None) -> BedrockContentBlock:
        """Synchronous image processing."""

        if "base64" in image_url:
            img_bytes, mime_type, image_format = cls._parse_base64_image(image_url)
        elif "http://" in image_url or "https://" in image_url:
            img_bytes, mime_type = BedrockImageProcessor.get_image_details(image_url)
            image_format = mime_type.split("/")[1]
        else:
            raise ValueError("Unsupported image type. Expected either image url or base64 encoded string")

        if format:
            mime_type = format
            image_format = mime_type.split("/")[1]

        image_format = cls._validate_format(mime_type, image_format)
        return cls._create_bedrock_block(img_bytes, mime_type, image_format)

    @classmethod
    async def process_image_async(cls, image_url: str, format: str | None) -> BedrockContentBlock:
        """Asynchronous image processing."""

        if "base64" in image_url:
            img_bytes, mime_type, image_format = cls._parse_base64_image(image_url)
        elif "http://" in image_url or "https://" in image_url:
            img_bytes, mime_type = await BedrockImageProcessor.get_image_details_async(image_url)
            image_format = mime_type.split("/")[1]
        else:

View on GitHub (pinned to 6c2dcb801b)

Solutions

1. Pass a proper data URI: "data:image/png;base64,<payload>" so the substring 'base64' is present.
2. Or pass a public http(s) URL that Bedrock can fetch.
3. If the image is local or in S3, fetch and base64-encode it yourself before building the message.
4. Verify the scheme is lowercase and matches the two supported branches exactly.

Example fix

// before
{"type": "image_url", "image_url": {"url": "/tmp/cat.png"}}
// after
import base64, pathlib
b64 = base64.b64encode(pathlib.Path("/tmp/cat.png").read_bytes()).decode()
{"type": "image_url", "image_url": {"url": f"data:image/png;base64,{b64}"}}

def is_bedrock_image_url_ok(url: str) -> bool:
    return "base64" in url or "http://" in url or "https://" in url

assert is_bedrock_image_url_ok(image_url), "Bedrock needs a data URI (with 'base64') or an http(s) URL"

def is_supported_image_url(url: str) -> bool:
    return isinstance(url, str) and ("base64" in url or url.startswith(("http://", "https://")))

try:
    resp = litellm.completion(model="bedrock/...", messages=msgs)
except ValueError as e:
    if "Unsupported image type" in str(e):
        image_url = local_image_to_data_uri(path)
        resp = litellm.completion(model="bedrock/...", messages=msgs)

When it happens

Trigger: Calling a Bedrock Converse model with a message content block {"type": "image_url", "image_url": {"url": ...}} where url is a local file path, an s3:// URI, a data URI missing the 'base64' label, or a bare base64 blob. Detection is substring-based: 'BASE64' uppercase or 'HTTP://' uppercase will not match.

Common situations: Porting Anthropic/OpenAI code that reads images from disk or S3; constructing data URIs manually and omitting ';base64'; using uppercase URL schemes; passing an OSS/HTTPS-variant scheme like 'HTTPS://'.

Related errors

• Unsupported content type: {type(content_block)}
• Bedrock Converse only supports base64-encoded document sourc
• Error: Unsupported image format. Format={_img_type}. Support
• Content type `{item_type}` is not supported by OCI
• model is required

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/ce331d7b68514f03. Report an issue: GitHub.