How do I disable firefox console from grouping duplicate output?

To solve this for any browser, you could use this workaround: Override the console.log command in window to make every subsequent line distinct from the previous line.

This includes toggling between prepending an invisible zero-width whitespace, prepending a timestamp, prepending a linenumber. See below for a few examples:

(function()
{
    var prefixconsole = function(key, fnc)
    {
        var c = window.console[key], i = 0;
        window.console[key] = function(str){c.call(window.console, fnc(i++) + str);};
    };

    // zero padding for linenumber
    var pad = function(s, n, c){s=s+'';while(s.length<n){s=c+s;}return s;};

    // just choose any of these, or make your own:
    var whitespace = function(i){return i%2 ? '\u200B' : ''};
    var linenumber = function(i){return pad(i, 6, '0') + ' ';};
    var timestamp = function(){return new Date().toISOString() + ' ';};

    // apply custom console (maybe also add warn, error, info)
    prefixconsole('log', whitespace); // or linenumber, timestamp, etc
})();

Be careful when you copy a log message with a zero-width whitespace.

As a workaround you can append a Math.random() to the log string. That should make all your output messages unique, which would cause them all to be printed. For example:

console.log(yourvariable+" "+Math.random());

Update [2022-01-24]

Seems like the below option doesn't work as expected. feel free to report it as a bug

Update [2020-01-28]

Firefox team added option to group similar messages, which is enabled by default.

You can access to this option via Console settings

• Open up Firefox's dev tools
• Select Console tab
• Click on gear button (placed at the right of the toolbar)
• Change the option as you wish

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Original Answer

As I mentioned in comment section, There is no way to achieve this at the moment. maybe you should try to request this feature via Bugzilla@Mozilla

Also you can check Gaps between Firebug and the Firefox DevTools

There is a settings menu () at the right of the Web Console's toolbar now which contains ✓ Group Similar Messages: