Image Compressor exists for a single, focused job that's distinct from format conversion: taking an image that's already in a perfectly fine format and making its file size dramatically smaller without a visible drop in quality. That distinction matters because compression and conversion often get conflated, but they're different operations solving different problems — the Image Converter tool on this site is for when you need a different file format; this tool is for when the format is already right but the file itself is too big for whatever you're trying to do with it: a website that's loading slowly because of oversized hero images, an email attachment bouncing against a provider's size cap, a photo gallery eating through cloud storage faster than it should.
The compression happening here works differently depending on which output format you choose, and understanding that difference is the key to getting good results instead of guessing at a slider. JPEG output uses lossy, discrete-cosine-transform compression — the same core approach JPEG has used since 1992 — which throws away visual information the human eye is comparatively bad at noticing (subtle color gradients, high-frequency texture detail) in exchange for large size reductions. WebP output uses a newer, more efficient prediction-based scheme that typically achieves 25-35% smaller files than JPEG at equivalent visual quality, because it predicts each block's pixel values from already-decoded neighboring blocks rather than compressing every block independently. PNG output, by contrast, is always lossless — it doesn't throw away any visual information, ever, regardless of what quality setting is shown — so choosing PNG here is really a choice to preserve exact pixel fidelity (and any transparency) at the cost of a much smaller size reduction than JPEG or WebP can achieve.
That's the trade-off at the center of this whole tool: quality and file size pull against each other, and the "right" setting depends entirely on what the image is for. A product photo destined for a fast-loading e-commerce page can usually drop to 65-75% JPEG quality with no visible difference to a typical shopper, saving 80% or more of the original file size. A photo being sent to a print shop for a large-format poster needs to stay much closer to 95-100% quality, where the file size savings are modest but the visual fidelity that print resolution demands stays intact. Compressing blindly at one fixed setting for every use case is how people end up either with visibly blocky images or with files that are still needlessly large — the slider exists because there genuinely isn't one correct number.
All of this compression work happens through the same browser-native mechanism used across this site's image tools: each source image is decoded to raw pixel data, drawn to an in-memory canvas, and re-encoded at your chosen format and quality using the browser's own image encoder. No image is ever transmitted to a server during that process, which matters for anything from unpublished product photography to personal photos you'd rather not route through a third party just to make the file smaller.
Need a different format instead of a smaller size? Image Converter is built for that, and Resize Image shrinks dimensions rather than just file size.
