siyuan-note/siyuan · error

unsupported custom emoji image format

Error message

unsupported custom emoji image format

What it means

Returned by normalizeCustomEmojiData as the final fallback: http.DetectContentType did not recognize the bytes as png/jpeg/gif/webp (raster=false) AND util.SanitizeSVG rejected the bytes as an SVG. The data is neither a supported raster nor a sanitizable SVG.

Source

Thrown at kernel/api/system.go:384

	case "image/webp":
		ext = ".webp"
	default:
		raster = false
	}
	if raster {
		config, _, decodeErr := image.DecodeConfig(bytes.NewReader(data))
		if decodeErr != nil || config.Width < 1 || config.Height < 1 || config.Width > 16384 || config.Height > 16384 ||
			int64(config.Width)*int64(config.Height) > 100*1000*1000 {
			return nil, "", fmt.Errorf("invalid custom emoji image")
		}
		return data, ext, nil
	}

	sanitizedSVG, sanitizeErr := util.SanitizeSVG(string(data))
	if sanitizeErr == nil {
		return []byte(sanitizedSVG), ".svg", nil
	}
	return nil, "", fmt.Errorf("unsupported custom emoji image format")
}

func normalizeCustomEmojiPath(name, ext string) (string, error) {
	name = strings.TrimSpace(strings.ReplaceAll(name, "\\", "/"))
	parts := strings.Split(name, "/")
	if len(parts) == 0 {
		return "", fmt.Errorf("custom emoji name must not be empty")
	}

	lastIndex := len(parts) - 1
	switch strings.ToLower(filepath.Ext(parts[lastIndex])) {
	case ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg":
		parts[lastIndex] = strings.TrimSuffix(parts[lastIndex], filepath.Ext(parts[lastIndex]))
	}
	for i, part := range parts {
		part = strings.TrimSpace(part)
		if part == "" || part == "." || part == ".." {
			return "", fmt.Errorf("invalid custom emoji name")

View on GitHub (pinned to 251596fc0d)

Solutions

1. Convert the image to one of png/jpeg/gif/webp, or to a clean hand-authored SVG.
2. If the source is SVG, remove <script>, on* handlers, external hrefs, and DOCTYPE/entity declarations, then retry.
3. Run the file through `file` to see its true type and re-export accordingly.

Example fix

// before
// uploading a BMP file -> 'unsupported custom emoji image format'

// after: convert to a supported format
//   convert emoji.bmp emoji.png   (ImageMagick)
// then upload emoji.png

// Confirm the content type is one of the accepted formats before uploading
ct := http.DetectContentType(data)
switch ct {
case "image/png", "image/jpeg", "image/gif", "image/webp":
    // ok raster
case "image/svg+xml", "text/xml; charset=utf-8":
    // candidate SVG; ensure it sanitizes
    if _, e := util.SanitizeSVG(string(data)); e != nil { return e }
default:
    return fmt.Errorf("unsupported content type %s", ct)
}

When it happens

Trigger: Uploading a BMP, TIFF, ICO, AVIF, HEIC, or a text/binary blob; or an SVG that fails sanitization (contains script, external refs, or malformed XML that SanitizeSVG rejects).

Common situations: User drops a .bmp or .tiff thinking it is supported; a SVG with embedded <script> or external entity that the sanitizer refuses; a file with a .svg extension but non-XML content.

Related errors

• custom emoji file is too large
• custom emoji file must not be empty
• invalid custom emoji image
• custom emoji name must not be empty
• invalid custom emoji name

AI-assisted analysis of siyuan-note/siyuan@251596fc0d (2026-08-12). Data as JSON: /api/errors/27012c04f9b390e9. Report an issue: GitHub.