Image Compressor

Every image file format makes a trade-off between file size and fidelity, and understanding that trade-off is the key to using a compressor effectively rather than just dragging a slider and hoping. Formats split into two broad families: lossless formats, like PNG, store every pixel's exact value and can always be decompressed back to bit-for-bit the same image, at the cost of larger files for photographic content; and lossy formats, like JPEG and (optionally) WebP, deliberately discard information a human eye is unlikely to notice — subtle colour gradients, fine texture detail in busy areas of a photo — in exchange for dramatically smaller files. This is precisely why PNG has no quality slider and JPEG does: PNG's compression is mathematically exact regardless of any setting, so there's nothing to trade away, while JPEG's entire design is built around a tunable quality parameter that controls exactly how much visual information gets discarded. JPEG achieves its compression primarily by splitting an image into small blocks and representing each block using a mathematical transform (a discrete cosine transform) that separates coarse, important visual detail from fine detail a viewer is less likely to consciously notice, then discarding more or less of that fine detail depending on the requested quality level. At quality 90-100, very little is discarded and the result is close to visually indistinguishable from the original at normal viewing sizes; at quality 50 and below, you'll start to see visible "blocky" artefacts, especially around sharp edges like text or strong contrast lines, because a meaningful share of the fine detail has been discarded to hit that file size target. WebP uses a more modern, generally more efficient lossy compression scheme, so at the same visual quality it typically produces smaller files than JPEG — one of the main reasons many websites have adopted it as a JPEG replacement for photos. Choosing the right format and quality is a matter of matching the image's actual content and your actual constraint. A photograph with smooth gradients and natural texture compresses well under lossy JPEG or WebP at a moderate-to-high quality, often shrinking to a fraction of its original size with no visible loss at normal viewing distance. A screenshot, logo, or image with large flat colour areas and sharp text edges, on the other hand, often compresses better and looks noticeably cleaner under PNG (or WebP's lossless mode) than under JPEG, because JPEG's block-based approach tends to introduce visible ringing artefacts around sharp, high-contrast edges — exactly the kind of content flat-colour graphics are made of. The most reliable way to choose a quality setting is to actually look at the before/after comparison rather than assume a number: this tool re-encodes the image live as you move the slider, so you can watch the file size drop and judge for yourself at what point the visual trade-off stops being worth it for your specific image and use case, rather than trusting a single rule of thumb that won't hold for every photo.