Images are often the heaviest part of a website. If they are unoptimised, they kill your page speed (a major ranking factor). Conversely, well-optimised images can drive significant traffic through Google Images, which is the world’s second-largest search engine.

Follow this workflow to ensure your visuals help, rather than hinder, your rankings.

1. Rename Files Before You Upload

Google’s AI can “see” images, but it still relies heavily on the text you provide to understand context. A file named IMG_8834.jpg tells Google nothing.

• The Action: Rename the file on your computer to describe exactly what is in the picture.
• The Format: Use lowercase letters and hyphens (not underscores) to separate words.
  • Bad: DCIM123.jpg
  • Good: bosch-boiler-installation-london.jpg
    
    

2. Write Descriptive Alt Text

“Alt text” (Alternative Text) is invisible text that describes an image for screen readers (used by visually impaired people). It is also the single most important data point for Google to understand your image.

• The Formula: Describe the image specifically, but do not stuff keywords. Imagine you are describing the photo to someone over the telephone.
  • Bad: “Boiler repair plumber heating.” (Keyword stuffing).
  • Good: “A gas engineer fixing a leak on a Worcester Bosch boiler in a kitchen.”
    
    

3. Compress and Convert (The “WebP” Standard)

You must reduce the file size without ruining the quality. A 5MB image from a professional camera will take seconds to load on a mobile phone, causing users to bounce.

• Compression: Run every image through a tool like TinyPNG or Squoosh before uploading. Aim for a file size under 100KB.
• Next-Gen Formats: Stop using standard JPEGs or PNGs where possible. Convert them to WebP, a modern format developed by Google that is significantly smaller but retains high quality. 
  
  

4. Enable Native Lazy Loading

Lazy loading stops the browser from loading images at the bottom of the page until the user actually scrolls down to them. This makes the initial page load much faster.

• The Action: Add the simple HTML attribute loading=”lazy” to your image tags.
  • Code: <img src=”boiler.webp” alt=”Boiler repair” loading=”lazy”>
• The Exception: Never lazy load the “Hero Image” (the first image at the top of the screen). This image must load immediately to satisfy Google’s “Largest Contentful Paint” (LCP) metric.
  
  

The Importance of “Alt Text”

Many people ignore Alt Text because it is invisible on the screen. However, Google has confirmed it is the primary way they index images.

“The most important attribute when it comes to providing more metadata for an image is the alt text… It also improves accessibility for people who can’t see images on web pages.”

If you skip Alt text, you are essentially hiding your images from Google. You are also failing accessibility standards (WCAG), which is a legal risk for many UK businesses.