Build a Privacy-First Image Compressor That Runs Entirely in Your Browser

The Problem Every online image compressor uploads your files to a server. That means: Your images pass through someone else's infrastructure Compression takes time due to upload/download Privacy-sensitive images (screenshots, documents) leave your device The Solution: Canvas API The HTML5 Canvas API can compress images entirely in the browser. No server. No upload. Your images never leave your device. Here's the core technique: function compressImage ( file , quality = 0.7 , maxWidth = 1920 ) { return new Promise (( resolve ) => { const img = new Image (); img . onload = () => { const canvas = document . createElement ( " canvas " ); let { width , height } = img ; // Resize if needed if ( width > maxWidth ) { height = ( height * maxWidth ) / width ; width = maxWidth ; } canvas . width = width ; canvas . height = height ; const ctx = canvas . getContext ( " 2d " ); ctx . drawImage ( img , 0 , 0 , width , height ); canvas . toBlob ( resolve , " image/jpeg " , quality ); }; img . src = UR