The console object provides access to the browser's debugging console (e.g. the Web Console in Firefox). The specifics of how it works varies from browser to browser, but there is a de facto set of features that are typically provided.

The console object can be accessed from any global object. Window on browsing scopes and WorkerGlobalScope as specific variants in workers via the property console. It's exposed as Window.console , and can be referenced as simply console . For example:

console.log("Failed to open the specified link")

This page documents the Methods available on the console object and gives a few Usage examples.

Note: This feature is available in This feature is available in Web Workers

Note: The actual console interface is defined as all lower case (i.e. not Console ), for historical reasons.

Methods

Examples

Outputting text to the console

The most frequently-used feature of the console is logging of text and other data. There are four categories of output you can generate, using the console.log() , console.info() , console.warn() , and console.error() methods respectively. Each of these results in output styled differently in the log, and you can use the filtering controls provided by your browser to only view the kinds of output that interest you.

There are two ways to use each of the output methods; you can simply pass in a list of objects whose string representations get concatenated into one string, then output to the console, or you can pass in a string containing zero or more substitution strings followed by a list of objects to replace them.

Outputting a single object

The simplest way to use the logging methods is to output a single object:

var someObject = { str: "Some text", id: 5 }; console.log(someObject);

The output looks something like this:

[09:27:13.475] ({str:"Some text", id:5})

Outputting multiple objects

You can also output multiple objects by simply listing them when calling the logging method, like this:

var car = "Dodge Charger"; var someObject = { str: "Some text", id: 5 }; console.info("My first car was a", car, ". The object is:", someObject);

This output will look like this:

[09:28:22.711] My first car was a Dodge Charger . The object is: ({str:"Some text", id:5})

Using string substitutions

When passing a string to one of the console object's methods that accepts a string (such as log() ), you may use these substitution strings:

%o or %O Outputs a JavaScript object. Clicking the object name opens more information about it in the inspector. %d or %i Outputs an integer. Number formatting is supported, for example console.log("Foo %.2d", 1.1) will output the number as two significant figures with a leading 0: Foo 01 %s Outputs a string. %f Outputs a floating-point value. Formatting is supported, for example console.log("Foo %.2f", 1.1) will output the number to 2 decimal places: Foo 1.10

Note: Precision formatting doesn't work in Chrome

Each of these pulls the next argument after the format string off the parameter list. For example:

for (var i=0; i<5; i++) { console.log("Hello, %s. You've called me %d times.", "Bob", i+1); }

The output looks like this:

[13:14:13.481] Hello, Bob. You've called me 1 times. [13:14:13.483] Hello, Bob. You've called me 2 times. [13:14:13.485] Hello, Bob. You've called me 3 times. [13:14:13.487] Hello, Bob. You've called me 4 times. [13:14:13.488] Hello, Bob. You've called me 5 times.

Styling console output

You can use the %c directive to apply a CSS style to console output:

console.log("This is %cMy stylish message", "color: yellow; font-style: italic; background-color: blue;padding: 2px");

The text before the directive will not be affected, but the text after the directive will be styled using the CSS declarations in the parameter.

The properties usable along with the %c syntax are as follows (at least, in Firefox — they may differ in other browsers):

background and its longhand equivalents.

and its longhand equivalents. border and its longhand equivalents

and its longhand equivalents border-radius

box-decoration-break

box-shadow

clear and float

and color

cursor

display

font and its longhand equivalents

and its longhand equivalents line-height

margin

outline and its longhand equivalents

and its longhand equivalents padding

text-* properties such as text-transform

properties such as white-space

word-spacing and word-break

and writing-mode

Note: The console message behaves like an inline element by default. To see the effects of padding , margin , etc. you should set it to for example display: inline-block .

Using groups in the console

You can use nested groups to help organize your output by visually combining related material. To create a new nested block, call console.group() . The console.groupCollapsed() method is similar but creates the new block collapsed, requiring the use of a disclosure button to open it for reading.

To exit the current group, simply call console.groupEnd() . For example, given this code:

console.log("This is the outer level"); console.group("First group"); console.log("In the first group"); console.group("Second group"); console.log("In the second group"); console.warn("Still in the second group"); console.groupEnd(); console.log("Back to the first group"); console.groupEnd(); console.debug("Back to the outer level");

The output looks like this:

Timers

You can start a timer to calculate the duration of a specific operation. To start one, call the console.time () method, giving it a name as the only parameter. To stop the timer, and to get the elapsed time in milliseconds, just call the console.timeEnd() method, again passing the timer's name as the parameter. Up to 10,000 timers can run simultaneously on a given page.

For example, given this code:

console.time("answer time"); alert("Click to continue"); console.timeLog("answer time"); alert("Do a bunch of other stuff..."); console.timeEnd("answer time");

Will log the time needed by the user to dismiss the alert box, log the time to the console, wait for the user to dismiss the second alert, and then log the ending time to the console:

Notice that the timer's name is displayed both when the timer is started and when it's stopped.

Note: It's important to note that if you're using this to log the timing for network traffic, the timer will report the total time for the transaction, while the time listed in the network panel is just the amount of time required for the header. If you have response body logging enabled, the time listed for the response header and body combined should match what you see in the console output.

Stack traces

The console object also supports outputting a stack trace; this will show you the call path taken to reach the point at which you call console.trace() . Given code like this:

function foo() { function bar() { console.trace(); } bar(); } foo();

The output in the console looks something like this:

Specifications

Specification Status Comment Console API Living Standard Initial definition.

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub Desktop Mobile Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet Console Chrome Full support 1 Edge Full support 12 Firefox Full support 2 IE Full support 8 Notes Full support 8 Notes Notes In Internet Explorer 8 and 9, the console object is undefined when the developer tools are not open. This behavior was fixed in Internet Explorer 10. Opera Full support 10.5 Safari Full support 3 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 4 Opera Android Full support 11 Safari iOS Full support 1 Samsung Internet Android Full support 1.0 assert Chrome Full support 1 Edge Full support 12 Firefox Full support 28 IE Full support 8 Opera Full support 11 Safari Full support 4 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 28 Opera Android Full support 11 Safari iOS Full support 3.2 Samsung Internet Android Full support 1.0 clear Chrome Full support Yes Edge Full support 12 Firefox Full support 48 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 48 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes count Chrome Full support Yes Edge Full support 12 Firefox Full support 30 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 30 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes countReset Chrome Full support Yes Edge Full support ≤79 Firefox Full support 62 IE No support No Opera Full support Yes Safari ? WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 62 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes debug Chrome Full support Yes Edge Full support 12 Firefox Full support 4 IE Full support Yes Opera ? Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes dir Experimental Chrome Full support 1 Edge Full support 12 Firefox Full support 8 IE Full support 9 Opera Full support 11 Safari Full support 4 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 8 Opera Android Full support 11 Safari iOS Full support 3.2 Samsung Internet Android Full support 1.0 dirxml Experimental Chrome Full support Yes Edge Full support 12 Firefox Full support Yes IE Full support Yes Opera Full support Yes Safari ? WebView Android Full support Yes Chrome Android Full support Yes Firefox Android No support No Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes error Chrome Full support 1 Edge Full support 12 Firefox Full support 4 IE Full support 8 Opera Full support 10.5 Safari Full support 3 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 4 Opera Android Full support 11 Safari iOS Full support 1 Samsung Internet Android Full support 1.0 exception (an alias for error ) Deprecated Non-standard Chrome No support No Edge No support 13 — 79 Firefox Full support 28 IE No support No Opera No support No Safari No support No WebView Android No support No Chrome Android No support No Firefox Android Full support 28 Opera Android ? Safari iOS No support No Samsung Internet Android No support No group Chrome Full support 1 Edge Full support 12 Firefox Full support 4 IE Full support 11 Opera Full support Yes Safari Full support 4 WebView Android Full support 37 Chrome Android Full support 18 Firefox Android Full support 4 Opera Android ? Safari iOS ? Samsung Internet Android Full support 1.0 groupCollapsed Chrome Full support 6 Edge Full support 12 Firefox Full support 52 IE Full support 11 Opera ? Safari Full support 5.1 WebView Android Full support 37 Chrome Android Full support 18 Firefox Android Full support 52 Opera Android ? Safari iOS ? Samsung Internet Android Full support 1.0 groupEnd Chrome Full support 1 Edge Full support 12 Firefox Full support 9 IE Full support 11 Opera Full support Yes Safari Full support 4 WebView Android Full support 37 Chrome Android Full support 18 Firefox Android Full support 9 Opera Android ? Safari iOS ? Samsung Internet Android Full support 1.0 info Chrome Full support Yes Edge Full support 12 Firefox Full support 4 IE Full support 8 Opera Full support Yes Safari Full support Yes Notes Full support Yes Notes Notes No information icon WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes log Chrome Full support 1 Edge Full support 12 Firefox Full support 4 IE Full support 8 Opera Full support 10.5 Safari Full support 3 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 4 Opera Android Full support 11 Safari iOS Full support 1 Samsung Internet Android Full support 1.0 profile Experimental Non-standard Chrome Full support 53 Edge Full support 12 Firefox Full support Yes IE Full support Yes Opera ? Safari ? WebView Android Full support 53 Chrome Android Full support 53 Firefox Android Full support 10 Opera Android ? Safari iOS ? Samsung Internet Android Full support 6.0 profileEnd Experimental Non-standard Chrome Full support Yes Edge Full support 12 Firefox Full support Yes IE Full support Yes Opera ? Safari ? WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 10 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes table Chrome Full support 27 Edge Full support 13 Firefox Full support 34 IE No support No Opera Full support 11 Safari Full support 6.1 WebView Android Full support ≤37 Chrome Android Full support 27 Firefox Android Full support 34 Opera Android Full support 11 Safari iOS Full support 7 Samsung Internet Android Full support 1.5 time Chrome Full support 1 Edge Full support 12 Firefox Full support 10 IE Full support 11 Opera Full support 11 Safari Full support 4 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 10 Opera Android Full support 11 Safari iOS Full support 3.2 Samsung Internet Android Full support 1.0 timeEnd Chrome Full support 1 Edge Full support 12 Firefox Full support 10 IE Full support 11 Opera Full support Yes Safari Full support 4 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 10 Opera Android ? Safari iOS ? Samsung Internet Android Full support 1.0 timeLog Chrome Full support 72 Edge Full support 79 Firefox Full support 62 IE No support No Opera Full support 60 Safari No support No Notes No support No Notes Notes See bug 186833. WebView Android Full support 72 Chrome Android Full support 72 Firefox Android Full support 62 Opera Android ? Safari iOS No support No Samsung Internet Android Full support 11.0 timestamp Experimental Non-standard Chrome Full support Yes Edge Full support 12 Firefox Full support Yes IE Full support 11 Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 10 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes trace Chrome Full support 1 Edge Full support 12 Firefox Full support 10 IE Full support 11 Opera Full support 11 Safari Full support 4 WebView Android Full support 1 Chrome Android Full support 18 Firefox Android Full support 10 Opera Android Full support 11 Safari iOS Full support 3.2 Samsung Internet Android Full support 1.0 warn Chrome Full support Yes Edge Full support 12 Firefox Full support 4 IE Full support 8 Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes Available in workers Chrome Full support Yes Edge Full support 12 Firefox Full support 38 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 38 Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes Legend Full support Full support No support No support Compatibility unknown Compatibility unknown Experimental. Expect behavior to change in the future. Experimental. Expect behavior to change in the future. 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 implementation notes. See implementation notes.

Notes

At least in Firefox, if a page defines a console object, that object overrides the one built into Firefox.

See also

Firefox Developer Tools

Web Console — how the Web Console in Firefox handles console API calls

Remote Debugging — how to see console output when the debugging target is a mobile device

Other implementations