1. Use the right size
Most of the saving comes from size, not compression. A photo straight from a phone is about 4000 pixels wide; a blog column is about 800. Resizing such a photo to the size it is shown cuts its weight by 90 percent or more before any compression.
In every compressor here, click Options and choose Resize: Max 1920px for full-width images, Max 1280px for content images, Max 800px for thumbnails. Images are only made smaller, never larger.
2. Use the right format
- Photos: JPG or, better, WebP. Convert with JPG to WebP for 25 to 35 percent smaller files.
- Logos, icons, screenshots: PNG or WebP. Both keep sharp edges and transparency.
- Never use PNG for large photos: it is lossless, so photos become huge.
Not sure? Read JPG vs PNG vs WebP.
3. Compress by a sensible amount
Each compressor has a Reduce size by setting under Options (50 percent by default). It finds the best quality that reaches that size, and only shrinks the pixel dimensions when quality alone is not enough.
- Compress JPG: 50 to 70 percent smaller is usually invisible on photos straight from a camera.
- Compress PNG: reduces the number of colours; 30 to 60 percent keeps graphics clean.
- Compress WebP: 30 to 50 percent, since WebP is already efficient.
The list shows the original and the new size of every file. All compressors handle many files at once and give you a ZIP. Camera data such as GPS location is removed too, which also saves a few kilobytes.
4. Check the result
Open the original and the compressed image side by side at 100 percent zoom. If you cannot see a difference, compress a little more; if you can, choose a smaller reduction. After uploading, test your page with a speed test such as PageSpeed Insights.
A quick checklist
- Resize to the displayed size.
- WebP for photos, PNG or WebP for graphics.
- Quality around 75 for photos, 85 for images with text.
- Descriptive file names and alt text for every image.