Image Optimizer — MozJPEG & OxiPNG Compression in Your Browser
Optimize JPEG with MozJPEG and PNG losslessly with OxiPNG, in batches, right in your browser. See before/after sizes and savings, then download files or a ZIP.
🔒 Runs entirely in your browser — nothing is uploadedSmaller JPEG and PNG files with professional encoders
Images are usually the heaviest part of a web page, and cameras, phones and design tools rarely save them as efficiently as they could. This image optimizer uses two of the best open-source encoders, compiled to WebAssembly so they run inside your browser: MozJPEG for JPEG photos and OxiPNG for PNG graphics. Both come from the same projects that power Google's Squoosh app. Drop a single file or a whole folder's worth of images, press Optimize, and a table shows the size before and after, the percentage saved and a download link for every file. When there are several files, you can grab them all at once as a ZIP archive.
Lossy JPEG versus lossless PNG
JPEG files are decoded and re-encoded with MozJPEG, which uses trellis quantisation and optimised Huffman tables to produce noticeably smaller files than a browser's built-in encoder at the same visual quality. This is lossy: choose a quality between about 75 and 85 for web photos, or higher for print. Progressive encoding is enabled by default so images appear quickly at low resolution and sharpen as they load. PNG files are handled completely differently: OxiPNG tries different filters and compression strategies and keeps the smallest result, while every pixel stays exactly the same. Higher optimization levels search more combinations and take longer. The optional cleanup of fully transparent pixels is invisible but often shrinks icons and logos further.
Safe defaults and full privacy
Some files are already optimized, and re-encoding them would make them bigger. By default the tool detects this and keeps your original file, so you never end up with a worse result. Because everything happens locally, there are no upload limits, no waiting for a server and no risk of private images being stored elsewhere. JPEG output does not keep EXIF metadata such as GPS location, which also saves a few kilobytes. For modern formats, try the AVIF converter or the WebP converter on this site.
How to use
- Add imagesDrop one or many JPG and PNG files.
- Set the optionsChoose the JPEG quality and progressive mode, and the PNG optimization level.
- OptimizePress Optimize and compare the before and after sizes for each file.
- DownloadSave files one by one or all together as a ZIP.