A website I work on has a partly transparent png image overlying parts of the website. The image is resized to 100% of the browser window width. In all other browsers the transparent parts behave normal – but safari shows a thin outline whee the image should be transparent.

I hope the screenshot makes the problem clear:

enter image description here

Now I'm wondering if this is this a bug – or a feature? And of course I would like to get rid of that zigzag line – so any suggestions and pointers are welcome. Thank you!


  1. Yes, I checked if the image has a grey line – but it does not.
  2. Also this problem anly appeared after I updated Safari to 11.0.2.
  3. And when modifying the img's width in dev tools first to the actual width (7000px) and then back to 100% the grey line disappears.
  4. Here is a link to the website where the problem appears.
  • Can you share the image itself? I suspect the grey outline is part of the image, stackoverflow.com/questions/19549498/…
    – grg
    Commented Jan 2, 2018 at 16:43
  • Please provide the URL to the actual image, not some screenshot. Commented Jan 2, 2018 at 16:48
  • Thank you for your suggestion. The image has however no grey line. Also this problem anly appeary after I updated Safari to 11.0.2. And when modifying the width in dev tools first to the actual width (7000px) and then back to 100% the grey line disappears. (updated the question accordingly) Commented Jan 2, 2018 at 16:58
  • I'm on Safari 11.0.1 and I'm not seeing any line. Definitely a bug though.
    – l008com
    Commented Mar 21, 2018 at 10:37

1 Answer 1


I just faced the same issue and stumbled upon this question.

For me, the image showed a thin, medium-dark, shadowy border at the edge between the non-transparent and the transparent part of the image. The issue was only visible in Safari.

Comparison of the rendered image with the thin border in safari and the original image with transparency visualized

For me, the solution was to simple add transform: translateZ(0px) to the image. This changes the rendering of the image in a way that prevents the border.

However, you might want to restrict this fix to Safari since it causes the image to be rendered pixelated in Chrome.

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