Images are the heaviest thing on most web pages. The average web page ships over a megabyte of images, and every extra kilobyte slows down loading, hurts your Core Web Vitals scores, and costs mobile visitors real data. The good news: you can usually cut image file sizes by 50 to 80 percent with no visible difference. If you want the one-click version, drop your files into our free image compressor and download the optimized versions.
Compression is not about picking one magic setting. It is a short pipeline: choose the right format, resize to the dimensions you actually display, then apply the right amount of compression for that format. This guide walks through each step, explains what the quality slider really does, and shows you how to verify the result with your own eyes.
Three reasons, in order of how much they cost you:
The fix is almost always worth more than the effort. An hour of image optimization routinely beats a week of other performance tweaks.
Format choice matters more than the quality slider. Each format is built for different content:
The most common mistake on the web is PNG screenshots and photos. A photographic PNG can easily be ten times larger than the equivalent JPEG or WebP. Rule of thumb: photos → JPEG or WebP; graphics with text → PNG or WebP; when in doubt → WebP.
This step is skipped constantly and it is the biggest lever you have. A 4000×3000 photo from a camera displayed at 800×600 on your page contains 25 times more pixels than anyone will ever see. No compression setting compensates for serving 25× the pixels.
Resize the image to the largest size it will actually display — then add a little headroom for high-density screens. Serving at 2× the CSS display size covers retina displays; 3× and beyond is wasted bytes. A hero displayed at 1200 px wide needs at most a 2400 px file, and usually 1600–2000 px is plenty.
For JPEG and lossy WebP, the quality slider (typically 0–100) controls how aggressively the encoder discards detail the eye barely notices. What the numbers mean in practice:
Start at 80 for JPEG or 75 for WebP and compare against the original at full size. If you cannot tell which is which, you are done — ship the smaller file. Our image compressor lets you preview the result before downloading, which makes this comparison trivial.
Lossy compression (JPEG, lossy WebP) throws away data permanently to shrink files. Lossless (PNG, lossless WebP) preserves every pixel exactly. For web delivery, lossy wins for anything photographic — the discarded data is detail humans cannot perceive at normal sizes.
Use lossless only when pixel-exactness matters: logos that must stay razor sharp, images containing small text, medical or technical imagery, and master files you plan to edit later. Never use lossless as your delivery format for photos; it is the single fastest way to bloat a page.
One important habit: always keep your original, uncompressed masters. Compression is one-way. If you compress a JPEG and later need a different size or higher quality, starting from the already-compressed file compounds the artifacts. Edit the master, export fresh.
srcset attribute lets the browser pick the right file size for the device. A phone gets the 800 px version, a desktop gets the 1600 px version, and nobody downloads more than they need:
<img src="photo-800.jpg"
srcset="photo-800.jpg 800w, photo-1600.jpg 1600w"
sizes="(max-width: 600px) 800px, 1600px"
alt="Description of the photo">loading="lazy" to below-the-fold images so they only download when the visitor scrolls near them. One attribute, large savings on long pages.Do not trust the settings blindly — verify:
The whole pipeline takes minutes per image: pick WebP (or JPEG for photos, PNG for sharp graphics), resize to 2× display size, compress at quality 75–80, lazy-load below the fold. Most sites can cut their image weight by more than half with zero visible change. It is the highest-ROI performance work you can do.
Start with your heaviest pages — run your images through our free image compressor and watch the kilobytes melt away.
WebP is the best default in 2026: 25–35% smaller than JPEG at equal quality, with transparency support, and universal browser support. Use JPEG for photos if you need maximum compatibility, PNG for graphics with sharp text, and AVIF for the smallest possible photo files.
Start at 80 for JPEG or 75 for WebP. This range is visually identical to the original for most photos at normal viewing sizes while cutting file size dramatically. Drop to 60–70 only for thumbnails where fine detail does not matter.
The opposite — it helps. Smaller images improve Largest Contentful Paint, one of Google's Core Web Vitals, and faster pages rank better and convert better. Just keep your alt text and filenames descriptive when you re-export.
Yes, always. Lossy compression is irreversible. Keep uncompressed masters so you can re-export at different sizes or quality levels later without compounding artifacts.
