Five hundred kilobytes is enough for a photo that looks essentially identical to the original on any screen, which makes it the usual limit on platforms that care about quality: property and product listings, blogs and website builders, photo contests and many email systems. A modern phone photo is 3 to 6 MB, so it still needs to shrink by around 85 to 90 percent, but most of that comes from compression the eye does not notice. This page opens with the target set to 500 KB. The tool searches for the highest JPG quality that fits and only reduces the dimensions if quality alone is not enough; a typical photo ends up around 1,800 to 2,400 pixels on the long side, still large enough for a full screen view or a modest print. For a website, that size is often larger than the page displays it, so resizing to the real display width with Image Resizer first and then compressing gives a smaller, faster file. WebP output reaches the same quality in fewer bytes if the destination accepts it. Batches are processed one image at a time with the result shown for each. The target is counted as 500,000 bytes. For a stricter limit see Compress Image to 200KB, and for a 1 MB limit Compress Image to 1MB.
Image compression is one of the highest-impact performance optimizations for most websites. Images typically account for 50 to 80 percent of a page's total download size, and unoptimized images are the most common cause of poor Core Web Vitals scores, particularly Largest Contentful Paint (LCP). A JPEG compressed to 75 percent quality is visually indistinguishable from the original for photographic content in most contexts, but can be 60 to 70 percent smaller. The human eye is much more sensitive to sharpness and color accuracy in certain areas (faces, text in images, sharp edges) than in others (smooth backgrounds, sky, blurred backgrounds). Lossy compression algorithms exploit this by applying heavier compression in less sensitive areas. For PNG files, lossless compression reorders pixel data and uses more efficient encoding tables. PNG compression level (1-9) trades CPU time for file size: higher levels take longer to encode but produce smaller files. For web use, both JPEG and PNG should be served at their maximum practical compression level (JPEG 75-85, PNG level 9) since the decompression time is negligible but the smaller network transfer size benefits every user. The recommended modern workflow for web image delivery is: optimize your original image with this tool, then serve it in WebP format for Chrome and Safari 14+ users with a JPEG fallback for older browsers using the HTML picture element with source type="image/webp".
Read our guide: In-depth guide for Compress Image to 500KB