You compress an image to reduce its file size, but when you open the result it looks soft, blurry, or blocky. This is one of the most common complaints about image compression — and it almost always has a fixable root cause. The goal of good compression is files that look identical to the original at a fraction of the size. Here are the five reasons that goes wrong, and how to fix each one.
JPEG and WebP compression work by discarding visual information the algorithm considers least noticeable. Set quality too low (below 70%) and the algorithm discards too much — you see the result as blurring, smearing, or 8×8 pixel blocking artifacts, especially around edges and in sky/gradient areas.
Fix: Use 75–85% quality for web photos. 80% is a reliable default that reduces file size by 60–80% with no perceptible quality loss. Going below 70% only saves an additional 5–10% in file size while visibly degrading the image.
Every time you save a lossy-compressed image (JPEG, WebP), the algorithm discards more detail. If you open a JPEG, edit it slightly, and re-save as JPEG, you've now run the lossy algorithm twice on the same image. The visual degradation compounds — artifacts from the first compression are treated as image data and get distorted further.
Fix: Always keep your original file in a lossless format (PNG, TIFF, or the camera's RAW file). Compress to JPEG only at the final export step, and only once. If you receive a JPEG and need to edit it, minimize re-saves — or accept that each re-save slightly reduces quality.
JPEG is designed for photographs with gradual color transitions. It handles sharp edges, text, and flat colors very poorly — compressing a screenshot or UI mockup as JPEG produces blurry text and blocky artifacts around icons and buttons. This isn't a quality-setting problem; it's a fundamental mismatch between the algorithm and the content type.
Fix: Use PNG or WebP lossless for screenshots, UI designs, and images with text. Use JPEG or WebP lossy only for photographs. Rule of thumb: if your image has hard edges or flat color regions, use PNG.
If you compress a 800×600px image and display it at 1600×1200px (or on a Retina/HiDPI display that expects 2× resolution), the browser has to scale the image up. Upscaling always blurs — pixels are being created where none existed. This is a display problem, not a compression problem, but it often gets blamed on compression.
Fix: Export at the resolution it will be displayed at, accounting for device pixel ratio. For Retina displays, export at 2× the CSS pixel dimensions. A card that's 400px wide in CSS should use an image that's 800px wide. Don't scale up after compressing.
Social media platforms, email clients, and CMSs often re-compress images on their servers after you upload them. If your original upload was already heavily compressed, the platform's re-compression amplifies existing artifacts and adds new blur. Instagram, LinkedIn, and Gmail are known for aggressive re-compression.
Fix: Upload the highest quality version you have to platforms that re-compress. Counter-intuitively, you get better results by uploading a larger, higher-quality file and letting the platform do the only compression pass. Don't pre-compress aggressively if you're going to upload to a re-compressing platform.
| Use Case | Format | Quality | Expected Size |
|---|---|---|---|
| Web photos (blog, portfolio) | JPEG or WebP | 80–85% | 50–200 KB |
| E-commerce product images | JPEG | 80–85% | 150–500 KB |
| Social media upload | JPEG | 90–95% (high quality) | 500 KB–2 MB |
| Email attachment | JPEG | 75–80% | 50–150 KB |
| Screenshots / UI | PNG | Lossless | 100–500 KB |
| Print (300 DPI) | JPEG or TIFF | 90–95% | 1–5 MB |
ImgMin's Balanced preset (80% quality) hits the optimal size-to-quality ratio for most use cases. No upload — your files stay private.
Try ImgMin Free →For web use, 75–85% quality hits the sweet spot — perceptually close to lossless but 60–80% smaller. For print, use 90–95%. For email attachments, 70–80% is fine. Going below 70% will produce visible blocking and blurring artifacts on most photos.
JPEG and WebP are lossy formats. Each time you save a lossy-compressed image, the algorithm discards more detail. Compressing an already-compressed JPEG a second time amplifies existing artifacts and introduces new ones — the visual degradation compounds. Always keep your original file and compress from scratch each time you need a smaller version.
Screenshots contain hard edges, text, and flat color regions — exactly what JPEG's DCT compression algorithm handles poorly. JPEG blurs sharp edges and introduces 8×8 pixel blocking artifacts on flat areas. Always save screenshots and UI mockups as PNG or WebP lossless. JPEG is designed for photographs, not graphics.