Compress Image

Why image file size matters

Large images are the single most common cause of slow web pages. Google's Core Web Vitals measure Largest Contentful Paint - the time until the main image on a page becomes visible. An unoptimised hero image at 3 MB can delay LCP by 3-5 seconds on a mobile connection. Compressing that same image to 200-400 KB typically makes the visual difference invisible while cutting load time dramatically.

Email clients have similar constraints. Most email services reject attachments above 10-25 MB and many subscribers open email on mobile data. Compressing photos before attaching them is good practice regardless of the email provider. For bulk workflows where you need to compress many files at once, the bulk resize tool lets you process up to 50 images and download them as a ZIP.

Understanding the quality slider

JPEG and WebP use lossy compression - they discard data that the human visual system is least sensitive to. The quality slider controls how aggressively data is discarded. At 85% most people cannot see any difference from the original. At 70% the file is typically 50-60% smaller with only faint softening in smooth gradients. Below 60% block artefacts become visible, especially on text and sharp edges.

The sweet spot for most use cases is 75-85%. Use 90%+ for professional photography portfolios where quality is paramount, and 65-75% for thumbnails, previews, and social media covers where a smaller download is worth a modest quality tradeoff.

Resize before you compress

Compression and resizing are complementary, not alternatives. If your image is 4000px wide and you only need 1200px, resize it first. You will get a much smaller file before compression even starts, and the compressed output will look sharper at the target display size. For a deeper look at quality settings and when to use each format, the guide on compressing images without losing quality walks through the tradeoffs in detail.