Convert MP4 to MP3 online

Convert MP4 to MP3 online in batches. Files stay in your browser and are never uploaded or stored on a server.

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Your files stay on this device and are never uploaded.

Drop files here to convert them

Up to 10 files · 100 MB each · 300 MB per batch

Choose MP4 files and convert them to MP3 together in one private browser session.

How to convert MP4 to MP3

Select one or more MP4 files, start the batch, then download each MP3 result or all completed files together.

This conversion extracts the audio track from each MP4 video and encodes it as MP3; it does not create video from audio.

Process up to 10 files per batch, with 100 MB per file and 300 MB in total.

The conversion runs locally in your browser. NDNCI never receives, stores, or sends your files to a third party.

Base32 Encoder/Decoder

Encode UTF-8 text to Base32 or decode Base32 values locally.

Base64 Encoder/Decoder

Encode or decode Base64 strings.

Image Converter

Convert PNG, JPEG, and WebP images in private browser-only batches with no uploads.

Markdown/HTML Converter

Convert between Markdown and HTML in both directions.

Spreadsheet Converter

Convert CSV and XLSX spreadsheets in private browser-only batches with no uploads.

URL Encoder/Decoder

Encode or decode URLs quickly.

Video Converter

Convert MP4, MOV, and WebM videos in private browser-only batches with no uploads.

Image Upscaler

Upscale images 2× locally, with optional AI acceleration and browser fallbacks.

Video Upscaler

Upscale videos 2× locally, using AI and WebGPU when available with a browser fallback.

3D Model Viewer

Open 3D models locally, inspect geometry, materials and textures, then download the original files.