Guide
How Image Compression Works (and How to Shrink Images)
Understand lossy vs. lossless compression, how quality affects size, and how to compress images for the web.
An image compressor shrinks PNG, JPG, or WebP files so they load faster on the web. It runs entirely in the browser, so your images never leave your device. Understanding the trade-offs helps you balance size and quality.
Lossy vs. lossless compression
Lossless compression (PNG) packs the same pixel data more efficiently with no quality loss, but file sizes stay relatively large. Lossy compression (JPG, WebP) discards visual detail that the eye barely notices, achieving much smaller files at the cost of some quality. WebP supports both modes and usually beats JPG and PNG at either.
How quality affects size
Lossy formats use a quality setting (typically 0–100). Lower quality means more data is discarded and a smaller file. For most web photos, quality 70–85 looks nearly identical to the original at a fraction of the size. Below 60, artefacts (blockiness, banding) become visible.
How to compress an image
- Upload or drop a PNG, JPG, or WebP file.
- Adjust the quality slider.
- Preview the result and the size savings.
- Download the compressed image.
Examples
A 3.5 MB photo saved as a high-quality JPG might compress to 600 KB at quality 80 with no visible difference, or 250 KB at quality 65 with minor artefacts. Converting that same photo to WebP at quality 80 could reach 450 KB — a further saving.
When an image compressor is useful
- Preparing images for a website or blog.
- Reducing email attachment sizes.
- Optimising product photos for an online store.
- Speeding up page loads to improve Core Web Vitals.
Put it into practice
Use the Image Compressor right now — free, in your browser, no sign-up required.
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