Beginner's Bible: Master WordPress image sizing and optimization methods to quickly improve site performance

Have you ever wondered why WordPress generates multiple size versions of your images when you upload them? Since visitors will access your website from different devices (laptops, smartphones, tablets), each with different screen sizes and resolutions, providing adapted image sizes is very important for smooth and efficient access.

1. What are WordPress image sizes?

pass (a bill or inspection etc)Media LibraryWhen uploading images, WordPress automatically generates the following default sizes:

• Thumbnail: For article featured images, photo albums or product listings.
• Medium: Suitable for the body of a blog, when full resolution is not required.
• Large: Used in scenarios such as top banner images that require clarity but do not unduly impact loading speed.
• Original size (Full): The original file uploaded, usually for large blocks of content.

Theme or plugin may registerCustom sizes(e.g. wide slideshow images for photography themes or product images for e-commerce plugins). All these versions take up server storage space.

2. Why do I need different image sizes?

Generating multiple versions may seem redundant, but each size serves a definite purpose:

• performance optimization: Smaller images load faster. Using "Medium" instead of the original image can increase page speed, improve SEO and user experience.
• Design Consistency: Themes and page builders rely on standard sizes to keep layouts uniform, whether it's a list of posts, photo albums, or product displays.
• responsive design: Different devices require different resolutions. Mobile is suitable for smaller sizes, while desktop uses a high-resolution version to enhance the visual effect.

These dimensions makeWordPressAutomatically adapts to the user's device without the need for manual adjustments.

3. How to disable unwanted image sizes

If certain sizes are not used, they can be disabled to save storage space by the following methods:

Method 1: Modify WordPress Settings

1. Access to the back office Settings > Media
2. Set the width and height of unwanted sizes (Thumbnail / Medium / Large) to0
3. After saving, new uploads will no longer generate these dimensions

Method 2: Modify the theme of thefunctions.phpfile
If the theme or plugin registers a custom size, you can add the following code to remove it:

function remove_unwanted_image_sizes() {
    remove_image_size('custom-size-name');
}
add_action('init', 'remove_unwanted_image_sizes'); }
function remove_unwanted_image_sizes() {
    remove_image_size('custom-size-name');
}
add_action('init', 'remove_unwanted_image_sizes'); }
function remove_unwanted_image_sizes() {
    remove_image_size('custom-size-name');
}
add_action('init', 'remove_unwanted_image_sizes'); }

Replace 'custom-size-name' with the actual size slug defined by your theme or plugin.

commander-in-chief (military)'custom-size-name'Replace with the actual size name (e.g.'portfolio-large').

Note: This action only affects future uploaded images. Sizes that have already been generated need to be deleted manually or processed using the Cleanup plugin.

4. How image optimization tools handle multiple sizes

as ifImage OptimizerThese tools automatically compress all sizes (including thumbnail/medium/large and custom sizes) to reduce file size while maintaining image quality. The optimization process is done automatically in the background without manual operation, which significantly improves website performance.

With Image Optimizer's settings panel, the compression range can be freely selected:

• Select all sizes for compression
• Or check only specific sizes (e.g. optimize only Large and Full sizes)
  This flexibility allows you to balance image quality with loading speed, optimized for critical sizes.

concluding remarks

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