Image compression is not a contest to produce the smallest possible file. The useful goal is to remove bytes that do not improve the image in its real viewing context. A product photo displayed at 720 pixels wide does not benefit from remaining 4,000 pixels wide, and a social thumbnail rarely needs the same quality setting as a portfolio image. If you want the conceptual difference between lossy and lossless encoding first, Lossy vs Lossless Image Compression covers that groundwork.
Start with the final display size
Dimensions usually matter more than a small quality adjustment. An image that is twice as wide and twice as tall contains four times as many pixels. If your layout never shows an image above 1,200 pixels, resize the source near that width before chasing encoder settings.
Keep high-resolution originals somewhere safe. Optimization should produce delivery copies, not replace the files you may need for printing, editing, or future layouts. The resize image tool creates new files and leaves originals untouched.
Pick a format that matches the content
JPEG remains a sensible choice for photographs. PNG is better for simple graphics, sharp interface captures, and transparency. WebP can work well for both photographs and graphics, but compare its real output rather than assuming it is always smaller.
Converting a screenshot with flat colors to a low-quality JPEG can introduce ringing around text. Keeping a large photograph as PNG can waste many bytes. Format choice is part of compression, not a separate afterthought.
Lower quality gradually
For lossy JPEG or WebP output, begin around 80–85 quality. Inspect faces, hair, foliage, fabric, gradients, and text overlays. These areas reveal damage sooner than smooth backgrounds. If the result looks clean at its actual display size, lower the setting in small steps.
Zooming to 400 percent can be useful for diagnosis, but it can also encourage oversized files. Visitors usually see the image inside a page, email, or message. Judge quality in that context too.
Avoid repeated lossy saves
Each lossy re-encode makes new decisions about which information to discard. Repeatedly opening a JPEG, saving it, and recompressing the new copy can accumulate artifacts. Return to the best available source whenever you need a new size or format.
The JPG compressor processes the selected original in one pass. If you change settings, it starts again from the queued source rather than compressing the previous result.
Check the result, not the promise
Some images are already optimized. A new encoder pass can produce little improvement or even a larger file, especially at a higher quality. A trustworthy workflow reports both sizes and lets you decide.
ImagesCompressor displays original and output dimensions, file sizes, and percentage saved for every completed image. When a result is larger, it says so. Try smaller dimensions, a different output format, or keep the original.
A reliable compression checklist
- Keep a backup of the original.
- Resize to the largest dimension the image really needs.
- Choose JPEG, PNG, or WebP based on the content.
- Start with moderate quality for lossy formats.
- Inspect the real use size and important detail areas.
- Compare file size and reject conversions that do not help.
Conclusion
Good compression is controlled subtraction. Remove unused dimensions, choose a suitable format, and reduce lossy quality only until the difference becomes noticeable. Use the reduce image size tool to test those changes locally without uploading the source file.