Free Image Compressor – Reduce JPG, PNG & WebP File Size Online

Image compression is the practice of reducing the number of bytes it takes to store a picture while keeping it visually acceptable. When you compress a photo for the web, you are exchanging a tiny amount of fine detail for a much faster download. On slow mobile connections that trade is almost always worth making.

Lossy vs lossless: the two ways to shrink

JPG uses lossy compression — it discards subtle gradients, noise and high-frequency detail that human eyes are poor at noticing, then relaxes the remaining data so it encodes in far fewer bits. PNG, by contrast, uses lossless compression: every pixel survives exactly, which is why PNGs of photos are huge. WebP cleverly supports both worlds, offering a lossy mode that beats JPG at the same size and a lossless mode that beats PNG. Most of the time you want lossy compression for photographs and reserve lossless modes for graphics, logos and transparent artwork.

What the quality slider actually changes

Lower quality lets the encoder drop more of that invisible detail. A 90% quality JPG of a landscape looks virtually identical to the original; a 30% version shows visible blocking. The trick is finding where your own eye stops noticing. For photos posted online, quality between 60 and 80 is a good starting point. For screenshots and diagrams, keep it at 80–90 since sharp text shows compression artifacts quickly.

Transparent PNGs have an extra constraint: flattening them to remove transparency shrinks them dramatically, but destroys any alpha channel. Big file, transparent subject, or smallest possible size — the slider helps you balance all three in one pass.

Finally, remember that compressing an already-compressed image costs quality instead of saving it. Always work from your original, highest-quality file, and you can recompress a photo many times without wrecking it.