usememos/memos · info

wrong image mediatype

Error message

wrong image mediatype

What it means

The image getter in internal/httpgetter downloaded the URL but the response mediatype did not start with image/, so the bytes are not treated as an image. Unlike the HTML path, this uses plain http.Get (no SSRF-hardened client) and checks only the prefix.

Source

Thrown at internal/httpgetter/image.go:32

}

func GetImage(urlStr string) (*Image, error) {
	if _, err := url.Parse(urlStr); err != nil {
		return nil, err
	}

	response, err := http.Get(urlStr)
	if err != nil {
		return nil, err
	}
	defer response.Body.Close()

	mediatype, err := getMediatype(response)
	if err != nil {
		return nil, err
	}
	if !strings.HasPrefix(mediatype, "image/") {
		return nil, errors.New("wrong image mediatype")
	}

	bodyBytes, err := io.ReadAll(response.Body)
	if err != nil {
		return nil, err
	}

	image := &Image{
		Blob:      bodyBytes,
		Mediatype: mediatype,
	}
	return image, nil
}

View on GitHub (pinned to 14d757ce1f)

Solutions

1. Use the direct image URL (ends in .png/.jpg or returns image/*), not the page URL
2. Verify with `curl -sI <url> | grep -i content-type`
3. If you own the server, serve the asset with a correct image/* Content-Type

Example fix

// before
GetImage("https://example.com/photos/cat") // HTML page
// after
GetImage("https://example.com/photos/cat.jpg")

// Verify the URL returns an image before downloading fully (HEAD)
func isImageURL(u string) bool {
  resp, err := http.Head(u)
  if err != nil { return false }
  return strings.HasPrefix(resp.Header.Get("Content-Type"), "image/")
}

// Fall back to a placeholder when the target is not an image
img, err := getter.GetImage(u)
if err != nil && strings.Contains(err.Error(), "wrong image mediatype") {
  img = placeholderImage(u)
  err = nil
}

When it happens

Trigger: Calling the image fetch with a URL returning text/html (an error page), application/json, application/octet-stream, or video/* content types; hotlink-protected servers returning an HTML login page.

Common situations: Fetching user-supplied avatar/OG-image URLs that are actually HTML pages; CDNs serving the wrong content type; copy-pasting page URLs instead of direct image URLs into image fields.

Related errors

• not a HTML page
• too many redirects
• internal IP addresses are not allowed
• hostname resolved to no addresses
• invalid URL format

AI-assisted analysis of usememos/memos@14d757ce1f (2026-08-15). Data as JSON: /api/errors/28170aa7f9ce7333. Report an issue: GitHub.