What this image compressor does
Phone photos are wonderful and enormous. A single shot from a modern phone can be four or five megabytes — fine on the phone, but miserable to email, slow to upload to a listing or a form, and quick to fill a free storage quota. This tool re-encodes your picture at a quality you choose, so the file shrinks while the picture still looks like the picture. You see the original size, the compressed size and exactly how much you saved before you download anything, and a comparison slider lets you wipe back and forth between the two versions to judge the quality with your own eyes instead of taking our word for it.
Everything happens on the picture itself, in your browser, using the same canvas technology your browser uses to display images. For photos, JPEG output at a quality around 0.75–0.85 is the sweet spot most people land on: the file is often 70–90% smaller, and at normal viewing sizes the difference is genuinely hard to spot. WebP output is frequently smaller again at the same quality. PNG output is offered because some images need it, but be aware PNG is lossless — it keeps every pixel exactly, which is why a PNG "compression" of a photograph can come out the same size or even larger. The tool tells you plainly when that happens and suggests a better setting, rather than quietly handing you a bigger file and calling it compressed.
How to compress an image
- Choose the image. JPG, PNG and WebP files from your device all work.
- Pick an output format. JPEG for photographs, WebP for the smallest modern files, PNG only when you need lossless.
- Set the quality. Start at 0.80. Lower numbers mean smaller files and softer detail; higher numbers keep more detail.
- Press Compress and compare the two previews with the slider. If text or faces look mushy, raise the quality a step and compress again — it takes a second.
- Download the result, named after your original file with "-compressed" added, so nothing gets overwritten.
Why quality settings behave the way they do
Lossy compression works by throwing away picture information your eyes are least likely to miss — fine texture in skies, subtle gradients, tiny noise between similar colors. At high quality settings it discards very little; at low settings it discards aggressively and you start to see blocky squares around edges and banding in smooth areas. Photographs tolerate this well because they are naturally noisy. Screenshots, diagrams and images with lots of crisp text tolerate it badly, because sharp edges are exactly what gets softened. For those, either keep the quality high (0.9 or above), choose PNG, or shrink the image's dimensions with our Image Resizer instead — a smaller picture is often a better answer than a more-compressed one.
One more honest note: a file that has already been compressed hard — a picture downloaded from social media, for example — has little left to give. Compressing it again saves almost nothing and can only soften it further. The savings figure this tool shows is the truth for your file, whether that is 85% or 2%.
Frequently asked questions
Is my image uploaded to a server to compress it?
No. The compression runs entirely in your web browser using its built-in image canvas. Your file is read on your device, re-encoded on your device, and downloaded from your device. Nothing is sent to TOOLS411 or anywhere else.
What quality setting should I use?
Start at 0.80 for photographs — most people cannot see the difference from the original at normal sizes, and the file is usually 70–90% smaller. Use 0.9 or higher for images with text or fine detail, and lower settings only when every kilobyte counts.
Why did my PNG come out bigger than the original?
PNG is a lossless format: it stores every pixel exactly, so re-encoding a photo as PNG has almost nothing it can throw away and the file can even grow. For photographs, choose JPEG or WebP output to actually shrink the file.
Will compressing hurt my photo's dimensions?
No. This tool keeps the exact same width and height — it only changes how the picture data is stored. If you want smaller dimensions as well, run the result through the Image Resizer.
Private by design: this compressor works entirely in your browser. Your image is never uploaded to a server — we could not look at your pictures if we wanted to.