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This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The dump() method of the WorkerGlobalScope interface allows you to write a message to stdout — i.e. in your terminal, in Firefox only. This is the same as Firefox's window.dump, but for workers.


dump('My message\n');


A DOMString containing the message you want to send.




To write an output from your worker to your computer's terminal, you first have to run an instance of Firefox started from your command line/terminal. For example, on Mac OS X you'd run it using something like this (assuming you are inside the Applications folder):

./ -profile /tmp -no-remote

Now go into about:config and enable the browser.dom.window.dump.enabled pref.

Next, run a worker containing the following line:


This should result in a "test" message being output to the terminal.


This method does not appear in any specification.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Chrome No support NoEdge No support NoFirefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoFirefox Android Full support 4Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support No


Full support  
Full support
No support  
No support
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.

See also