Batch Change File Extensions

Change file extensions in bulk. Convert .txt to .md, unify case, and more.

How It Works

Upload files, specify the new extension or transformation rule (e.g., uppercase all extensions), preview, and download. All processing is local.

Common Use Cases

Convert .txt files to .md for Markdown editors
Fix incorrect extensions (e.g., .jpeg → .jpg)
Standardize extension casing (.PNG → .png)
Batch add extensions to files missing them

Privacy & Security

All file processing happens entirely in your browser. Your files are never uploaded to any server, never stored, and never transmitted over the internet. We cannot see or access your files.

This tool uses modern browser APIs to read and process files locally. Downloaded files are packaged as a ZIP archive and saved directly to your computer.