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Copper (Cu) CoAP user-agent

Implements RFC7252

Also see Copper (Cu4Cr)

Not supported by Firefox 56+ / WebExtensions API

Mozilla changed their add-on model to the WebExtensions API, which does not allow implementing protocol handlers.

Copper cannot be fixed to work again unless Mozilla changes the internals of Firefox again -- not to the old one, but a safe one that allows for protocol handler add-ons.


  • Copper4Cr: Chrome also uses the WebExtensions API, but has a loophole through discontinued Apps installed in developer mode
  • Californium (Cf) Browser: Java-based tool, yet without the debug options support
  • Firefox 55 Portable: Downgrade, but only use for add-ons, not browsing...
    1. Ensure to start offline (no Internet connection!) and disable auto updates
    2. Open about:config
    3. Search browser.tabs.remote.autostart and browser.tabs.remote.autostart.2
    4. Set both to false

A Firefox add-on to browse the Internet of Things

How to integrate the Copper sources into Firefox:

  1. Get the sources from Github: clone git://
  2. Add a text file named to your extension directory of your profile:
  • Windows: C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxxxxx.default\extensions\
  • Linux: ~/.mozilla/firefox/xxxxxxxx.default/extensions/
  • MacOS: ~/Library/Application Support/Firefox/Profiles/xxxxxxxx.default/extensions/
  1. Write the path to the Copper sources (i.e., the directory that contains install.rdf and chrome.manifest) with (back)slash at the end to the file (e.g., D:\Projects\Git\Copper\).
  2. Since Firefox 43 you need to allow unsigned add-ons by opening about:config and setting xpinstall.signatures.required to false.
  3. Restart Firefox.
  4. Optionally use about:config with the filter "copper" to clean up old configurations.

Copper should show up in the add-ons list. You can now enter CoAP URIs (e.g., coap:// into the address bar and will have a user interface to interact with the CoAP resources on a server. The detailed log output is available through the rectangular button on the top right, next to the preferences button.

See also:


Copper (Cu) CoAP user-agent (JavaScript implementation)







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