A Simple Guide To Image Compression For SEO

data being transferred on a laptopNovember 17, 2025
Honestly, image compression is something that should be completed out of the box, and is best automated. However, if you've got some large images on your website that are slowing down the page speed, then we've put together a simple guide to optimising them for SEO and Core Web Vitals.

The Best Settings For Image Compression

This is your overall aim for a compressed image, there is a bit of give and take, as long as your images aren't massive, you should be okay.
  • Most images should be compressed to between 80 KB and 250 KB depending on purpose
  • WebP is the recommended format for most modern websites
  • Hero landscape images should be no more than 1920px wide
  • Portrait images typically look best around 1200 px height
  • Standard content images are ideally 1024px wide for landscape, or 1024px in height for portrait

Recommended Tools

For quick and reliable compression, these tools work well for most users:
  • squoosh.app for single image compression
  • bulkimagecompressor.com for compressing multiple images at once
  • reSmush.it plugin for WordPress websites needing built in optimisation

Step By Step Guide To Compressing Images

This guide is for single image compression for Squoosh. However, it also works much the same for Bulk Image Compressor.

Step One: Choose An Image

Select an image, and determine if it is landscape or portrait. This is important because if you set the width of a hero image to 1920px and it's a portrait, you'll end up with a much larger height and therefore bigger image due to Squoosh's native retention of aspect ratio. Once you've achieved this, simply drag and drop your image into Squoosh.

Step Two: Set Your Dimensions

In the column on your right, click the resize option. This will allow you to set the width or height of your image. Only set width for landscape, or height for portrait as this will automatically scale the other to retain the aspect ratio and scale.

Step Three: Change Your Format

Most images will natively come in either PNG or JPEG format. Most modern browsers now accept WebP format, which is better for page speed. Under 'compression' in the right column of Squoosh, simply select the WebP format.

Step Four: Download & Edit Your Image

Squoosh will automatically compress and change the image size once you've selected your settings. Download the image with the button in the right hand corner and change the name to one that is relevant. This is particularly important if it's a stock image.

Step Five: Upload Your Image

Finally, upload your image to your platform, whether that’s WordPress, Shopify or any CMS, you’ll want to add an alt text describing the image for accessibility and SEO good practice. We go into more detail about alt text below.

Squoosh example

Understanding Image Compression

Image compression reduces the file size of an image while trying to preserve as much visual quality as possible. There are two main types of compression. Lossy compression removes some visual information to achieve a smaller file size, while lossless compression maintains quality but may not reduce the size significantly. For most websites, lossy compression provides better performance benefits without noticeable quality loss.

Search engines reward websites that load quickly. Compressed images help improve Core Web Vitals such as Largest Contentful Paint. Faster pages mean better user experience, lower bandwidth usage and a higher chance of ranking well, especially on mobile devices.

Choosing The Right Format

JPEG is suitable for photographs because it compresses well without major quality loss. PNG is best for graphics, text or images requiring transparency, although the file sizes can be larger. WebP has become the recommended option because it offers superior compression compared to JPEG and PNG. Most modern browsers support WebP, making it ideal for both photos and graphics.

Recommended Dimensions For Website Images

Hero banners are often displayed large, so a width of 1600 to 2000 px is usually enough. Blog feature images typically look good around 1200 px width. Thumbnails and small graphics can be anywhere from 300 to 600 px depending on placement. Product photos should be large enough to show detail, often between 1200 and 1600 px on the longest side.

Landscape images offer more horizontal space, making them suitable for banners and featured sections. Portrait images work well for blog content and product layouts where vertical orientation is required. Choosing dimensions that match your layout prevents unnecessary file size.

Alt Text & File Naming

Alt text helps search engines understand what an image represents, supports accessibility and assists with ranking for image search. Keep alt text descriptive and accurate. File naming also contributes to SEO. Use clear, keyword relevant names such as cardiff cafe interior.jpg rather than generic strings of numbers.

Local SEO benefits greatly from properly named images. If your photo shows a location or landmark in your service area, naming the file appropriately helps search engines connect your site with that location.

Contact Our Professional Team Today

Image compression is a quick win for SEO and user experience. By using the right formats, choosing appropriate sizes and following a consistent process, you can significantly improve your website’s performance without sacrificing visual quality.

If you need help optimising your website or improving your SEO performance, Formwork Digital is here to support you.

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