Why are WordPress images not showing up with HTTPS?

Question

I'm facing a strange problem with SSL, in fact all my images didn't showing up on SSL, this is an example:

HTTP : http://www.electronique-mixte.fr/wp-content/uploads/2017/06/numidea-logo-electronique-mixte.png

HTTPS : https://www.electronique-mixte.fr/wp-content/uploads/2017/06/numidea-logo-electronique-mixte.png

For the same picture, the HTTP is working, but the HTTPS is not!

Website :

HTTPS picture 404 error:

HTTP working fine:

Another browser (Edge):

PS : I'm using incognito tab (avoid cache)

Answer 1

Because no one else mentioned this: since this is in WordPress (based on the URL structure), make sure your "Site Address" and "WordPress Address" include "https" in the URL:

Located in Settings > General.

Because WordPress uses these fields to generate image URLs, it's important to include the "https" here, even if you're otherwise redirecting to HTTPS (such as through Apache or Nginx).

Answer 2

Add meta tag in your theme header:

<meta http-equiv="Content-Security-Policy" content="upgrade-insecure-requests">