Do images smaller than default optimal size load slower?

  • Hi. I always size the pics I upload to my posts as 1024×568, which I believe is the optimal size for fast loading on my site.

    However, I am currently writing a post where the image I want to display is narrow and the closest I can get it to the optimal size as specified above is 375×568.

    My question is, when images are smaller than optimal size like this, do they still have to be resized by WP when published to the web, and therefore load slower? Or is the load time of smaller images unaffected? I know that images larger than the optimal size load slower unless resized appropriately. Just not sure about smaller ones.

    Cheers
    Ross

    The page I need help with: [log in to see the link]

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  • That would be a question for the theme developer. If you place images with the add media button then the images are sized by the theme. If you upload the images the exact size you want them to appear and code them manually they are not resized by the theme.

    Uh, the theme is not resizing images.
    WordPress generates various sizes when the image is uploaded, based on your media size settings. The theme can influence the srcset attribute that is used. The browser chooses from that.

    I’m not sure what you mean by optimal size. That would be different for different devices and how the image is used in the page.

    Thread Starter RossB

    (@rossb)

    Hello guys and thanks for your responses. My understanding based on my research years ago when I first started using the Twenty Fourteen theme is that that theme uses 2 custom media sizes:
    672x372px for post thumbnail image size and 1038x576px for ‘twentyfourteen-full-width’ custom image size. I altered my Twenty Fourteen child theme post width to 1024px. I was advised by helpful folk on here to re-size all images I wish to upload to 1024×576, and “let theme resize them.” I am not a technical person (obviously), but had had excellent advice from these folk before, so have followed it ever since.

    My understanding based on advice received is that image sizes other than 1024×576 are re-sized by my Twenty Fourteen child theme via html/css properties. I was also under the impression that when testing the page speed on Pingdom etc, the page load speed is reduced by images that are not 1024×576, indicated by the message: “The following images are resized in HTML or CSS”.

    I hope that clarifies my understanding (or misunderstanding) and my question. In the hope that it has, I ask my question again, re-phrased:
    For images smaller than 1024×568, such as the 375×576 one I want to upload for the post I am currently writing, will this be resized via html/css properties and therefore take longer to load when someone opens the post?

    If yes, to prevent this resizing taking place, should I do something like place the image inside a 1024×576 rectangle using Photoshop or whatever, so it is recognised as 1024×576 and therefore not resized? I’m just trying to optimise image load time on my posts – that’s the only objective and the reason behind my question.

    Actually, also, I wonder if someone would mind checking my site and ascertaining whether that 1024×576 image size is the custom media size for my child theme. It has just struck me that I might have misinterpreted previous advice and have been using the wrong size all along! I know I should know how to do this stuff myself, but I retain very little of technicals and always seem to struggle to find answers when “researching” with Google.

    Cheers
    Ross

    • This reply was modified 6 years, 2 months ago by RossB.
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