Image Compression and Optimization Not Working in Bolt App
Your Bolt.new application loads images at full resolution regardless of display size, causing slow page loads, excessive bandwidth usage, and poor Core Web Vitals scores. A 5MB profile photo is served at 4000x3000 pixels even though it's displayed at 100x100 on the page.
Bolt's AI typically generates basic img tags or stores images exactly as uploaded without any processing. This means a user uploading a 10MB DSLR photo gets that exact 10MB file served to every visitor, even on slow mobile connections.
The problem compounds quickly: a page with 20 user-uploaded images can require 50MB+ of downloads, making your app unusable on mobile and destroying your Google PageSpeed score. Image optimization is one of the biggest performance wins for any web application.
Error Messages You Might See
Common Causes
- No image processing on upload — Images are stored at original resolution and format without server-side resizing or compression
- Missing Next.js Image component — Using plain <img> tags instead of Next.js <Image> which provides automatic optimization
- No lazy loading — All images load eagerly on page load, even those below the fold that aren't visible yet
- Wrong image format — Serving PNG or JPEG instead of modern WebP or AVIF formats that are 30-50% smaller
- No responsive sizing — Serving the same large image regardless of the user's screen size or viewport
How to Fix It
- Use Next.js Image component — Replace <img> with <Image> which auto-optimizes: <Image src={url} width={400} height={300} quality={80} />
- Compress on upload — Process images server-side before storage using sharp: sharp(buffer).resize(1200, 1200, { fit: 'inside' }).webp({ quality: 80 }).toBuffer()
- Use Supabase image transforms — Serve optimized images via transform URL: supabase.storage.from('images').getPublicUrl(path, { transform: { width: 400, quality: 80 } })
- Add lazy loading — Add loading="lazy" to images below the fold, or use the IntersectionObserver API for custom lazy loading
- Generate multiple sizes — Create thumbnail, medium, and full-size versions on upload and serve the appropriate one using srcset
- Set proper cache headers — Configure Cache-Control: public, max-age=31536000, immutable for static image assets
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Get HelpFrequently Asked Questions
What image format should I use for web?
Use WebP as the default format - it provides 30% smaller files than JPEG at the same quality. For maximum compression, use AVIF (50% smaller than JPEG). Always provide a JPEG fallback for older browsers using the picture element.
How do I optimize images already in my storage bucket?
Use Supabase's built-in image transformation API to serve optimized versions without re-uploading. Add transform parameters to your getPublicUrl call: { transform: { width: 800, format: 'webp', quality: 75 } }.