The Caesium app and MCP server
Shrink photos and images for email, websites and upload limits — compress, resize and convert to JPG or WebP, a whole folder at a time.
Free · no account · 3 free uses of every tool · also for Mac (Intel), Windows, Linux
Part of GUI Hub Essentials.
Make photos and images smaller. Compressed copies go to a folder you choose; originals stay untouched.
Compress every image in a folder (and optionally its subfolders) in one go.
GUI Hub gives your assistant these 2 tools. Install it once (below) and ask in plain words.
| MCP tool | What it does | Inputs |
|---|---|---|
| caesium_compress | Compress, resize and/or convert image files (JPG, PNG, WebP, GIF, TIFF) on the user's computer. Writes compressed copies (same file names) into outDir; never modifies originals or overwrites existing files. Use mode=size with maxSize (bytes) to fit upload limits. | inputs* array mode string quality string maxSize string resize string format string exif boolean outDir* string |
| caesium_folder | Compress, resize and/or convert every image in a folder on the user's computer, optionally including subfolders (folder structure is kept). Copies go to outDir; originals are never modified. | folder* string recursive boolean mode string quality string maxSize string resize string format string exif boolean outDir* string |
* required
Free to try — 3 full uses of every tool.
Download the one-file GUI Hub Essentials extension, double-click it, press Install. Done — ask Claude.
Download for ClaudeAdd an MCP server with this command (needs Node.js 18+):
npx -y https://guihub.cc/mcp.tgz --product=essentials
Claude Code:
claude mcp add gui-hub-essentials -- npx -y https://guihub.cc/mcp.tgz --product=essentials
Point-and-click forms for every Essentials tool, plus a Use with AI button that connects Claude Desktop or Cursor for you.
Download for WindowsNew independent apps get this one-time caution.
“Compress images” runs the official Caesium 1.5.0 program with arguments passed directly — never through a shell.
caesiumclt --quality 80 --no-upscale --format original --output /Users/you/out --overwrite never /Users/you/a.pdf /Users/you/b.pdf
Use Image Compressor 3 times free. $9 once unlocks all of GUI Hub Essentials.
Every tool works 3 times free first. Secure checkout by Polar; your license key arrives by email — paste it into the app, or just give it to your AI. 30-day refunds.
Powered by Caesium 1.5.0 (Apache-2.0), downloaded from its official release and verified by SHA-256. GUI Hub is independent and not affiliated with Caesium.