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I want to be entirely clear about this, what I'd like to do is change the size of the featured image thumbnail on the ADMIN panel, not on the front end.

I'm building a WP-admin theme, and I need to make the featured image larger on the back end.

It seems, featured images in the edit-post screen always spit out at 266x148px, ideally I'd like them to be actual size. I've searched around and can't find any hooks or functions that'd let me do this, but if anyone knows how, it's the people on here.

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Once this happened to me as a bug (images showing in actual size rather than resized in the Featured Image meta box). And it was not nice, they were blowing out of the window viewport. – brasofilo Jun 29 '13 at 3:03

1 Answer 1

You can filter 'admin_post_thumbnail_html' and replace the img element with a new one in the size you need.

Everything else will get messy and might lead to side effects.

  • Filtering image_downsize while watching for a size of 266×266 might affect images that are not meant to be shown in the metabox.
  • Changing the size for post-thumbnail temporary is not easy, because there are no safe points to start and end such a filter.
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Are you saying it's better not to do it? – andy Jun 28 '13 at 23:43
No, I just listed two other ways and why I think they aren’t better. – toscho Jun 28 '13 at 23:52
Ah ok. But does filtering it allow me to have the size as auto? – andy Jun 29 '13 at 0:07
I can figure out how to change the html in the box, but not the image itself. add_filter( 'admin_post_thumbnail_html', 'add_featured_image_instruction'); function add_featured_image_instruction( $content ) { return $content .= '<p>This is the featured image</p>'; } – andy Jun 29 '13 at 0:16
I would also like to do this, here's my related question:… – Sol Sep 16 '14 at 2:44

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