I built a free file converter with Next.js + FastAPI + FFmpeg — here's how

I got tired of every "free" file converter requiring signup, adding watermarks, or limiting conversions. So I built my own. What it does FileConvertTool converts files between 30+ formats: Images: PNG, JPG, WebP, HEIC, AVIF, SVG, GIF, BMP, TIFF, ICO Video → Audio: MP4, MOV, MKV, AVI, WebM → MP3, WAV, AAC, OGG Audio: MP3, WAV, FLAC, AAC, OGG, WMA, M4A Tools: Image compression, SVG tracing (raster to vector) No signup. No watermarks. No daily limits. Files are encrypted and auto-deleted after conversion. Tech stack Frontend: Next.js 15 (static export) → Cloudflare Pages Zero server costs for the frontend Global CDN, fast loading everywhere Static export means no Node.js server needed Backend API: Python FastAPI on Railway FFmpeg for video/audio processing Pillow + pillow-heif for image conversion (including HEIC/AVIF) vtracer for SVG tracing (raster → vector) CairoSVG for SVG → raster conversion Why this stack? FFmpeg is the most powerful media processing tool in existence. It handles vi