explaingit

xifangczy/cat-catch

Analysis updated 2026-06-21

★ 19,604JavaScriptAudience · generalComplexity · 1/5LicenseSetup · easy

TLDR

A browser extension for Chrome, Edge, and Firefox that surfaces videos and audio streams silently loading on any web page, so you can inspect and download them directly.

Mindmap

mindmap
  root((repo))
    What it does
      Detects media streams
      Lists video and audio
      Enables direct download
    Formats supported
      HLS M3U8
      DASH MPD
      Direct video files
    Tech
      JavaScript
      hls.js
      StreamSaver.js
    Platforms
      Chrome extension
      Edge extension
      Firefox extension
    Use cases
      Download authorized video
      Inspect page media
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Code map

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filefunction / class

What do people build with it?

USE CASE 1

Download a streaming video from a web page you are authorized to save.

USE CASE 2

Extract an M3U8 or DASH stream URL from a video site for offline viewing.

USE CASE 3

Inspect what media resources a web page is loading in the background.

What is it built with?

JavaScripthls.jsmux.jsStreamSaver.js

How does it compare?

xifangczy/cat-catchnuysoft/mocktesting-library/react-testing-library
Stars19,60419,62219,582
LanguageJavaScriptJavaScriptJavaScript
Setup difficultyeasyeasyeasy
Complexity1/52/52/5
Audiencegeneraldeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Primary documentation is in Chinese, English and Spanish READMEs are also provided.

You can use and share this freely, but any modified version you distribute must also be open-source under the same GPL-3.0 terms.

In plain English

Cat-catch is a browser extension for Chrome, Edge, and Firefox that sniffs out and lists the media resources (videos, audio, M3U8 streaming files) loaded by the current web page. When you visit a streaming site or a page with embedded video, the browser silently downloads many pieces in the background, cat-catch intercepts those and shows them to you so you can download the content directly. Think of it as a way to surface what your browser is already loading, making it easy to save a video you own or are authorized to download. The extension is written in JavaScript and works by inspecting network requests made by the page. It includes a built-in M3U8 parser, M3U8 is the format used by HLS, the streaming technology behind most modern video platforms, along with support for MPD (DASH streaming format). It uses established open-source libraries including hls.js, mux.js, and StreamSaver.js to handle parsing and saving. All data is processed locally in the browser, nothing is sent to a remote server. Installation is available via the official Chrome Web Store, Microsoft Edge Add-ons store, and Firefox Add-ons store, or directly from the source code for development use. The project is licensed under GPL-3.0 and is primarily documented in Chinese, though English and Spanish READMEs are also provided. The authors note that the extension should only be used to download content the user owns or has permission to download.

Copy-paste prompts

Prompt 1
I have cat-catch installed. How do I use it to download an HLS video stream from a page where there is no visible download button?
Prompt 2
How do I build on cat-catch's source code to add support for a custom streaming format my site uses?
Prompt 3
Explain how cat-catch's M3U8 parser works and how I can extend it to handle encrypted HLS streams.

Frequently asked questions

What is cat-catch?

A browser extension for Chrome, Edge, and Firefox that surfaces videos and audio streams silently loading on any web page, so you can inspect and download them directly.

What language is cat-catch written in?

Mainly JavaScript. The stack also includes JavaScript, hls.js, mux.js.

What license does cat-catch use?

You can use and share this freely, but any modified version you distribute must also be open-source under the same GPL-3.0 terms.

How hard is cat-catch to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is cat-catch for?

Mainly general.

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