Is it really 100% offline?

Yes. Once installed, 1FileTool processes every single file entirely on your computer. There are no server calls, no uploads, no cloud processing. Your files never leave your device, ever.

What file formats are supported?

1FileTool supports 100+ file formats including PDF, JPG, PNG, WebP, SVG, GIF, MP4, MOV, AVI, MKV, MP3, WAV, FLAC, AAC, ZIP, CSV, XLSX, JSON, XML, HTML, Markdown, and many more.

Is there a free version?

Yes. 1FileTool is free to use with all 265+ tools and up to 8 files per day. Upgrade to Pro for unlimited processing with a one-time payment starting at $29.

How is this different from online tools like Smallpdf?

Online tools require uploading your files to their servers for processing. 1FileTool processes everything locally on your device, so your files never leave your computer. Plus, you pay once instead of monthly.

Does it work on both Mac and Windows?

Yes. 1FileTool is available as a native application for both macOS (Apple Silicon and Intel) and Windows (64-bit) with identical functionality.

Can an AI assistant use 1FileTool?

Yes. AI Access exposes 64 operations to Claude Code, Codex and Gemini over MCP. You ask for the work in plain language and your assistant sends instructions to the app on your machine — your files are never sent to the assistant.

Does the AI run on my computer?

Yes. Background removal, read-aloud, audiobook conversion, voice cleanup and PII detection all run on your device after a one-time model download. There is no AI API key and no per-use cost.

All Tools / File Tools / Change Extension

Change Extension

Change file extensions in bulk

File ToolsWeb Demo Available

Try Change Extension Online

Browser File Workflow

No files selected

Files stay in your browser tab. For filesystem automation, archive extraction, and zip workflows, use the desktop app.

How To Use Change Extension Offline

Open 1FileTool — Download and install the app on your Mac, Windows or Linux computer. Select Change Extension from the File Tools category or search for it with Cmd+K.
Drop your file — Drag and drop your file into the tool. You can also paste from clipboard or select multiple files for batch processing. Everything stays on your device.
Get your result — Click process and your file is ready instantly. No uploads, no waiting for servers, no data leaving your computer.

Why Use 1FileTool Over Online Tools?

100% offline — Files never leave your computer. No uploads, ever.
Pay once — One-time payment from $29. No monthly subscriptions.
Instant results — Local processing is faster than uploading + server processing + downloading.
No file size limits — Process files of any size, limited only by your disk space.
GDPR compliant — No data collection means complete privacy compliance by design.

Change Extension

Try Change Extension Online

How To Use Change Extension Offline

Why Use 1FileTool Over Online Tools?

Related File Tools

Create ZIP

Extract Archive

ZIP

Rename

Rename by Pattern

Add Prefix

Keep the next file job off the internet.