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Lymphatus

Lymphatus/caesium-app-web

A browser-based image compressor for JPG, PNG and WebP that works fully offline, so images never leave your device.

Open-source alternative to:TinyPNGSquoosh

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128
Forks
17
Open issues
1
Last commit
4 months ago

What is it?

Caesium Web is a web app for compressing images. It runs entirely in the browser, powered by the libcaesium-wasm WebAssembly build, so files are processed locally and are not uploaded or handled by any external server. The app can be used offline once loaded.

It supports JPG, PNG and WebP images, with both lossy and lossless compression modes. Image metadata is kept during compression, and a before/after comparison view lets you check the result against the original.

For self-hosting, the project includes a Dockerfile and runs with npm for development and production builds. Several environment variables control the batch file limit, the maximum file size, and whether usage statistics are sent to a configurable endpoint.

Key features

  • 01Compresses JPG, PNG and WebP images
  • 02Supports both lossy and lossless compression
  • 03Keeps image metadata after compression
  • 04Before/after comparison view
  • 05Processes images locally in the browser, with offline use after loading

Use cases

  • Shrinking photos before uploading them to a website or sending by email
  • Compressing images for privacy-sensitive material that should not go to a third-party service
  • Batch-reducing image sizes with a self-hosted Docker deployment

Quick start

  1. 1

    Install dependencies

    npm install
  2. 2

    Start the development server on localhost:3000

    npm run dev

Things to know

  • Usage stats are sent to an endpoint by default; set NUXT_PUBLIC_SEND_USAGE_REPORT to false to disable it.

Topics

#image-compression#webassembly#browser#offline#privacy#docker#nuxt

FAQ

What is caesium-app-web?
A browser-based image compressor for JPG, PNG and WebP that works fully offline, so images never leave your device. Caesium Web is a web app for compressing images. It runs entirely in the browser, powered by the libcaesium-wasm WebAssembly build, so files are processed locally and are not uploaded or handled by any external server. The app can be used offline once loaded.
Is caesium-app-web free to use? What license does it have?
caesium-app-web is open source under the MIT license. Check the license terms before using it in commercial products.
Is caesium-app-web still maintained?
Updated within 6 months. The last commit to caesium-app-web was on Jun 20, 2026.
What can I use caesium-app-web for?
Shrinking photos before uploading them to a website or sending by email Compressing images for privacy-sensitive material that should not go to a third-party service Batch-reducing image sizes with a self-hosted Docker deployment
How do I install caesium-app-web?
Install dependencies: npm install Start the development server on localhost:3000: npm run dev
Where can I get caesium-app-web?
The source code and installation instructions are on GitHub: https://github.com/Lymphatus/caesium-app-web

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