It seems to be a feature and not a bug: screen sizes are not added to scrset if you upload a gif as teaser image: https://core.trac.wordpress.org/ticket/34528 This applies only to teaser images and not images in the article.
I used 8-Bit PNG instead and now all scrset attributes are filled.
Related Posts:
- Pb with responsive image sizes in WP 4.4
- How do I disable responsive images in WP 4.4?
- make WordPress image captions responsive
- WP 4.4. responsive images browser choosing the “wrong” one
- the_post_thumbnail responsive srcset not populating with custom image size
- How to insert pictures without hard coded dimensions?
- Responsive Theme Design: how have slideshow on desktops/tablets and static photo on mobile using same template?
- Create image formats with different qualities when uploading
- How can I set image sizes and still have responsive images using the srcset attribute?
- How to get attachment id of background image?
- Responsive Images
- WP 4.4. responsive loads normal image after loading the responsive image
- Why is wp_get_attachment_image_src returning wrong dimensions? [duplicate]
- Making WordPress Gallery (.gallery-item) Responsive?
- Featured Image in 4.4 should be larger on mobile device
- WP 4.4 aspect ratio with responsive image
- How to use the responsive images feature from WP 4.4 in your themes
- Generating Responsive Background Image Sizes in PHP
- How can I serve different images depending on screen size with wordpress
- Change function in responsive theme
- How to Make WordPress Default gallery responsive on mobile?
- wordpress responsive image srcset not working
- Responsive background images added inline
- $content_width for responsive UI
- Responsive Images – Add srcset attributes to custom Images Function
- Get a list of all image sizes that match aspect ratio of original one
- How to exclude an image size from the WordPress srcset
- Get specific image size for small viewport width
- How do I make featured images retreived by the_post_thumbnail() responsive?
- Responsive Images Resizing Images
- ACF Plugin – Random Gallery Image with wp_get_attachment_image()
- Featured image (responsive) above content is too small after update to WordPress 4.4
- How to display a different image size for mobile
- Responsive 2 column staggered layout client expectations vs reality problem
- WP Responsive images – upload custom image sizes
- Responsive Video Max-width
- Fuzzy Images in WordPress 4.4
- Removing height and width from images with a caption
- How to create ‘Local’ filters for WordPress srcset sizes in template parts?
- Multiple amp-image overlays. How to properly do this in wordpress?
- Fallback for missing srcset images
- max_srcset_image_width doesn’t work as intended
- CSS: How can I show a photo beyond the template’s column, but contained within the browser window? [closed]
- ACF Wysiwyg Editor Image srcset for responsive images [closed]
- adaptive featured images wordpress 4.4 grid
- Using SRCSET with Images and Featured Images
- Modify ‘Sizes’ Attribute for Images with Specific Class
- Responsive Images – crop don’t seem to work
- Responsive Images Warping
- How to force the twentyfourteen narrow screen layout to apply to wide screens?
- twentythirteen h1 and h2 not resizing responsively
- Custom image size vs CSS sizing
- Change Responsive Images Maximum Width of 1600px
- Understanding WordPress image sizes and responsive images
- Custom responsive ‘featured image’ sizes
- One of my image sizes isn’t showing up in srcset
- srcset and custom field get_post_meta and wp_get_attachment_url
- YouTube video goes over sidebar [closed]
- Where are the src and srcset sizes coming from?
- How to stop WordPress from completely overriding my tags in my templates?
- How to accept images at multiple sizes and aspect ratios and display as standardized image size / ratio?
- Adding srcset to an image in ajax
- the_content not showing responsive image attributes srcset or sizes
- Serve different images per screen size and cache possible?
- Disable Media File Image Link On Mobile Devices
- Wp_List_Table not responsive
- Generate responsive post thumbnails of same size
- All 3?: Responsive resizing of images + image width of actual image for small images + max-width for all larger images
- mobile vs responsive sites [closed]
- Change Image Sizes for Mobile Theme
- Why does WordPress list all image sizes in srcset even if they’re larger?
- Responsive header image
- What’s are some best practices for responsive images (e.g. for section headers)?
- Configure WordPress to Use Responsive Image Rendering
- Responsive Theme Design: how have slideshow on desktops/tablets and static photo on mobile using same template?
- responsive not working
- I want to add “View Desktop Version” for mobile visitors for my wordpress site
- WordPress Responsive Image ( srcset ) not work properly
- WordPress 5: including larger thumbnail image sizes in srcset than I have set
- Responsive Images – Defining
- Decide how Hero image appears on mobile
- Responsive Featured Images Not Working
- Responsive images with srcset
- Getting extra image links in code with wp_get_attachment_image
- built-in responsive images in content – do I need to add anything to functions.php?
- Responsive Images with art direction
- Responsive images in Bootstrap 4 slider
- WordPress not choosing the right image from srcset
- Responsive Images in WordPress
- Navigation Menu Rendering Issue on Windows 10
- Header Logo Scaling
- nextgen pro horizontal filmstrip moves up as browser narrows
- Filter the_content() to add custom figure tags
- The hyperlink not responsive with post? [closed]
- Create various image sizes ad hoc
- Trouble with responsivitizing my twentythirteen header
- site is loading fully zoomed in on mobile devices
- Is there a good way to use CMS images with CSS
- Show content based on width?
- making images scalable for responsive designs [closed]