Large images slow down websites and get rejected by upload forms. This guide explains how compression works and how to cut the file size without a visible drop in quality.
Why image size matters
Images are usually the heaviest part of a web page. Oversized pictures make pages load slowly, especially on mobile data, and slow pages lose visitors. Outside the web the problem is more direct: job portals, exam forms and visa applications often refuse photos above a fixed limit such as 100 KB or 200 KB.
Lossless and lossy compression
Lossless compression makes a file smaller without changing a single pixel. PNG works this way, and it is the right choice for logos and screenshots. Lossy compression, used by JPG, throws away fine detail that the eye barely notices and gets much smaller files in return. The skill is choosing a setting where the saving is large and the loss cannot be seen.
Compress a photo in three steps
Open the Compress Image tool and choose your file. Leave the quality slider near 70 percent for a good balance, or type a target size in KB if a form gives you a limit. Press Compress and download. The tool shows the new size next to the original so you can see how much was saved.
Which quality setting to use
Between 60 and 80 percent, most photographs look the same as the original while the file shrinks to a fraction of its size. Below about 40 percent, blocky patches and halos appear around edges and text. If you need a very small file, reduce the pixel dimensions first: a 4000 px wide photo shown in an 800 px space carries detail nobody will see.
Good habits for web images
Resize pictures to the size they will be shown at before compressing them. Use JPG for photographs and PNG for graphics that need sharp edges or transparency. WEBP gives smaller files than JPG at similar quality and is supported by all current browsers. Keep an untouched copy of the original, because every lossy save removes a little more detail.