Large images are the most common cause of slow pages.
- Resize images to the dimensions they're actually displayed at — don't upload a 4000px photo for a 600px slot.
- Compress them before uploading using a tool like TinyPNG or Squoosh.
- Use modern formats like WebP where possible.
- WordPress: an image optimisation plugin (for example, Smush or ShortPixel) compresses images automatically on upload.
- Enable lazy loading so images load only as visitors scroll to them.
Tip: Optimising images often gives the single biggest speed improvement for the least effort.
