Konvert - Professional File Converter
A privacy-first file converter that runs entirely in your browser. No uploads, no servers just drag a file in and convert it locally with FFmpeg WebAssembly.
Key Features
Privacy-First
100% client-side
Lightning Fast
Instant conversion
40+ Formats
Images, video, audio
PWA Ready
Mobile optimized
Technology Stack
Frontend & Core
Processing & Libraries
How It Works
Client-Side Conversion
Everything runs in the browser using FFmpeg WebAssembly. That means your files never leave your device, and you can still get full FFmpeg-level conversions without a backend.
FFmpeg WebAssembly Integration
I load FFmpeg from a CDN, initialize it in the browser, and route each conversion through format-specific commands.
// FFmpeg initialization
export default async function loadFfmpeg(): Promise<FFmpeg> {
const ffmpeg = new FFmpeg();
const baseURL = "https://unpkg.com/@ffmpeg/core@0.12.2/dist/umd";
await ffmpeg.load({
coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, "text/javascript"),
wasmURL: await toBlobURL(`${baseURL}/ffmpeg-core.wasm`, "application/wasm"),
});
return ffmpeg;
}
// Format-specific conversion
export default async function convert(ffmpeg: FFmpeg, action: Action) {
const { file, to, file_name } = action;
const input = getFileExtension(file_name);
const output = removeFileExtension(file_name) + "." + to;
// Format-specific FFmpeg commands
let ffmpeg_cmd: any = [];
if (to === "3gp") {
ffmpeg_cmd = ["-i", input, "-r", "20", "-s", "352x288"];
} else if (["jpg", "jpeg", "png"].includes(to.toLowerCase())) {
ffmpeg_cmd = ["-i", input, output];
}
// ... more format handling
}Supported File Formats
Konvert supports 40+ file formats across images, videos, and audio, including modern formats like WebP, AVIF, and HEIC.
Image Formats (20+)
- JPG ↔ PNG (transparency support)
- PNG ↔ WebP (modern optimization)
- WebP ↔ AVIF (next-gen formats)
- HEIC → JPG/PNG (iPhone compatibility)
- BMP ↔ TIFF (professional imaging)
- SVG → Raster (vector conversion)
Video Formats (15+)
- MP4 ↔ AVI (cross-platform)
- MOV ↔ WebM (Apple to web)
- MKV ↔ MP4 (streaming compatibility)
- FLV → Modern (legacy upgrading)
- 3GP → MP4 (mobile enhancement)
- WMV → MP4 (Windows Media)
Audio Formats (12+)
- MP3 ↔ WAV (quality vs size)
- FLAC ↔ MP3 (lossless to compressed)
- OGG ↔ AAC (open source to standard)
- M4A ↔ MP3 (Apple to universal)
- WMA → Modern (Windows Media)
- AIFF ↔ WAV (professional audio)
Performance & UX
Real-Time Processing
Files convert in the browser with real-time progress and batch processing. You can queue multiple files and watch each one update as it goes.
// Real-time progress tracking
const [actions, setActions] = useState<Action[]>([]);
const [is_loaded, setIsLoaded] = useState<boolean>(false);
const [is_converting, setIsConverting] = useState<boolean>(false);
// Batch processing support
const convertFiles = async () => {
for (const action of actions) {
setActions((prev) =>
prev.map((a) => (a === action ? { ...a, is_converting: true } : a))
);
// Process file with progress updates...
}
};Challenges
The hardest part was getting FFmpeg to load reliably in the browser without blowing up memory. Large files can crash a tab fast if you don't stream and clean up properly.
Another challenge was handling dozens of formats without overwhelming the UI. I ended up building format-specific command builders and a simple preset system so users don't have to think about encoding flags.