How to Resize WordPress Images Automatically (2 Methods)

Last updated on Aug 28, 2024 by Southie Williamson

Are your WordPress images too large? If you don’t resize your photos before uploading them, you can end up with a very slow website. Large, high-resolution images, while visually appealing, can significantly increase your site’s loading speed, especially if your website contains lots of photos.

Slow-loading sites annoy users and can negatively impact your search engine rankings since site speed is a crucial SEO factor. However, resizing images manually can be time-consuming. Thankfully, there’s a way to automate the process.

In this guide, we’ll show you how to resize WordPress images automatically to save time, enhance site speed, and ensure your pictures are always displayed perfectly.

Can you resize images for WordPress?

Yes, there are several methods to resize images for WordPress, each with its own benefits and use cases:

• Manual Resizing: WordPress offers the ability to resize individual photos and perform basic edits using the image block. The only problem with this method is that you must manually resize every picture after uploading it, which can take a long time. If you’d like to use this method to scale one-off photos, check out our tutorial on quickly editing images in WordPress.
• Optimizing Before Upload: Another option is to optimize your images before uploading them to WordPress using editing software or online tools. While helpful for some users, this requires additional steps outside of WordPress. You can check out our articles on the best free image compressors and how to batch-resize images in Photoshop to learn more.
• Automatic Resizing Using Plugins: Lastly, there’s a third option, which allows you to upload your images to WordPress as-is and then bulk resize them automatically using a plugin. This is ideal for users who want to maintain site performance without manually resizing each image or relying on outside software. 

So, without further ado, let’s look at how to auto-resize WordPress images.

How to Automatically Resize Images for WordPress

Several plugins can help automate image resizing on your WordPress site. Today, we’ll look at 2 different options.

Method 1: Automatically Resize Images in a Gallery

In the first method, we’ll use Envira Gallery, a powerful tool for creating galleries and managing your WordPress images.

The plugin can automatically resize or crop photos that are added to a gallery. This allows you to serve scaled images to visitors in various layouts like fullscreen, masonry, mosaic, slideshow, polaroid, and more, making it ideal for anyone needing to resize and display multiple images.

By default, Envira Gallery is fully responsive and mobile-friendly. This means it automatically scales images to fit in their galleries and ensures they look great on all devices. Moreover, the plugin lets you further optimize images by setting your own custom dimensions for desktop galleries, mobile galleries, lightbox views, and thumbnails.

Plus, Envira Gallery offers tons of other features to help you manage and display your website visuals, including:

• Video galleries with automatic thumbnails and a lightbox player
• Built-in image compression, lazy-loading, and deep linking to improve SEO
• Albums to manage and display multiple galleries
• Tags to organize your WordPress images and create filterable galleries
• Social media sharing
• Dynamic galleries to display content from other sources like featured blog posts, testimonials, Instagram posts, and more.
• And so much more!

See All of Envira Gallery’s Features →

Step 1: Install Envira Gallery

First, you’ll need to Install and Activate Envira Gallery on your WordPress site. The free version of the plugin will let you resize the gallery or lightbox view. However, you’ll want to grab a Pro license to access all our features, such as fullscreen images, custom thumbnail sizes in the lightbox, WooCommerce integration, and more.

You can see our step-by-step documentation if you’re unfamiliar with installing a WordPress plugin. Once Envira Gallery is activated on your site, you’re ready to create your first gallery.

If you’re using a premium license, you’ll also want to go to Envira Gallery » Settings from your WP admin menu and enter your license key to unlock all available features and addons.  

Step 2: Create a New Image Gallery

After activating Envira Gallery, you can create a new image gallery by navigating to Envira Gallery » Add New. Enter a title for your gallery and upload or select photos from your Media Library.

For more detailed instructions, check out our beginner’s guide to creating an image gallery. Next, we’ll show you how to adjust your settings to resize images.

Step 3: Configure Image Size Settings

To resize or crop images automatically within your gallery, scroll down to the Gallery Settings panel and click Configuration from the menu on the left.

Here, you’ll see an option for Image Size. You can use the dropdown menu to automatically resize photos to one of the preset WordPress sizes. Or, select Default and enter the maximum size you want to use next to Image Dimensions.

By default, images will be resized to maintain their aspect ratio. However, to enable cropping, check the box next to Crop Images. This will auto-crop your photos to exactly match the size you defined. Once enabled, you can use the Crop Position dropdown to specify where images are cropped from.

Pro Tip: Want to resize images for mobile? Click the Mobile tab, enable it, and customize the image size you want to generate for mobile galleries.

Step 4: Resize Lightbox Images

Regardless of the size you set for your gallery, Envira will display images in their original size when opened in a lightbox. To change this, click the Lightbox tab on the left. Then, select one of your preset WordPress sizes using the dropdown menu next to Image Size.

These sizes are predetermined by your site settings and theme. You can learn more about this in How to Disable or Add Custom Image Sizes in WordPress.

Premium users can also Enable Gallery Thumbnails to provide a better navigation experience for visitors viewing photos in a lightbox or slideshow. If enabled, you can select Use Custom Width/Height to customize the thumbnail sizes within the lightbox.

Once you’ve finished creating your gallery, be sure to click Publish.

Step 5: Embed Your Resized Image Gallery

You can easily embed the gallery anywhere on your site using a shortcode or Envira’s native Gutenberg block. You’ll also be able to quickly add images to your gallery and adjust basic things like your layout style, columns, and margins using the block settings sidebar within the WordPress editor.

Once embedded, you can rest easy knowing all the images will be resized and displayed according to your preferences. Only want to display a few photos from a larger gallery? Check out this documentation.

Ta-da, you learned how to auto-resize images in a gallery!

Pro Tip: Use Envira Gallery’s Defaults Addon to bulk-apply resizing and other settings to multiple galleries.

Method 2: Resize Multiple Images in Your WP Media Library

In the second method, we’ll show you how to resize WordPress images using Imsanity, a free image resize plugin.

This simple, free plugin uses WordPress’s default resizing functionality to automatically scale and replace WordPress images in your Media Library. It can resize your photos to specified dimensions upon upload or resize previously uploaded photos.

Step 1: Install Imsanity

To start, you’ll need to install and activate the Imsanity plugin. Go to Plugins » Add New Plugin in your WordPress menu and search for Imsanity. When you see it, click the Install Now button.

When the button changes to Activate, click it.

Step 2: Configure Settings to Auto-Resize on Upload

Next, go to Settings » Imsanity and adjust the settings for resizing your WordPress images:

• Images uploaded within a Page/Post: Enter the max width and height for photos uploaded within a WordPress page or post. You can set it to “0” to ignore. For example, you may want to make images the same size as the maximum width of your blog post area with auto-height using 0.
• Images uploaded directly to the Media Library: Set a size (or 0 to disable) for all photos uploaded via Media » Add New Media File.  
• Images uploaded elsewhere: Set a size (or 0 to disable) for all other uploaded photos, such as backgrounds, theme headers, and logos.

You can also select the JPG image quality for compression and decide whether or not to automatically convert BMP and PNG images to JPG. Note that the plugin uses standard WordPress compression, so you shouldn’t rely on this alone when optimizing images.

Lastly, decide whether or not to Delete Images. If enabled, the plugin will fully replace the initially uploaded image with the scaled-down photo in the new file format (if converted). WordPress will use this new version to generate thumbnails.

Once you’re satisfied with your settings, click the Save Changes button. Now, Imsanity will automatically resize all your large images to the sizes you set, and you don’t need to do a thing.

Step 3: Resize Already Uploaded Images

If you have large photos uploaded before installing Imsanity, you can also use the plugin to resize them individually or all in one go. Both options will use the dimensions you set for Images uploaded within a Page/Post in the previous step, so first, ensure that’s set to the size you want to use. Then…

To resize an image individually:

• Go to Media » Library in your admin menu and click the icon to switch to List View.
• Click the Resize Image button next to any photo you want to scale down.

Do note that there’s no way to apply a bulk action to select and resize multiple images.

To resize ALL of your images at once…

• On the Settings » Imsanity screen, scroll down to the Bulk Resize Images section.
• Carefully read the warning message, which explains why it’s important to backup your images before bulk resizing them.
• When you’re ready to proceed, click Start Resizing All Images and then OK to confirm.

Remember to backup your images BEFORE you click “Start Resizing All Images.” Once resized, you won’t be able to revert back to the original images.

That’s it!

We hope this article helped you to learn how to resize WordPress images automatically. That way, you can maintain an optimized, fast-loading website that keeps visitors happy and improves your SEO rankings.

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If you enjoyed this article, you may want to check out our Ultimate Guide to the Best Web Hosting for Photographers.

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