About this tool
About Image Compressor
Reduce image file size before uploading, emailing or publishing while keeping enough visual quality for the destination. Image Compressor lets you compare the result in your browser and download a smaller copy without replacing the original.
What image compression changes
Compression reduces the amount of data needed to store an image. Lossy formats such as JPG can remove subtle detail to produce much smaller files. Lossless formats preserve decoded pixel information but may not shrink photographic images as dramatically. The useful target is not the smallest possible number—it is the smallest file that still looks acceptable at the size where people will view it.
Photographs usually tolerate moderate compression better than screenshots, interface captures and graphics containing small text. Check faces, hair, gradients and dark areas in photos. For screenshots and logos, inspect text edges, flat colors and transparency for ringing or blur.
Compression versus resizing and conversion
If an image is physically larger than the website will display, resize it before or during compression. A 4000-pixel photo does not need to remain 4000 pixels wide when the layout shows it at 1000 pixels. If the current format is inefficient for the destination, converting PNG or JPG to WebP may produce a better web result than lowering quality repeatedly.
How to compress an image online
- Add a supported image and note its original file size and dimensions.
- Choose the available quality, format or dimension settings.
- Process a sample and compare it with the source at the intended display size.
- Look for blockiness, halos, banding, blurred text or broken transparency.
- Download the compressed copy and test it against the actual upload limit.
Real-world uses
Compress product images before adding them to an online store, reduce article graphics to improve page speed, prepare photographs for application forms, or make email attachments easier to send. For a batch, use one representative image to choose the quality setting, then inspect several results rather than assuming every image responds to compression in the same way.
Privacy and processing limits
Supported compression runs locally in your browser when available, so the source does not need to be uploaded to zer.ai. Large pixel dimensions and large batches still require browser memory. Keep an original master because repeated lossy compression can accumulate visible damage.
Use Image Resizer when dimensions are the main issue, Image Converter when the destination requires another format, or Remove Image Metadata when embedded camera or location information is the concern.