Client-side JavaScript logging library for Logmatic.io

Usage no npm install needed!

<script type="module">
  import logmaticJs from 'https://cdn.skypack.dev/logmatic-js';



Link to the Logmatic.io documentation

Client-side JavaScript logging library for Logmatic.io.


  • Use the library as a logger. Everything is forwarded to Logmatic.io as JSON documents.
  • Metas and extra attributes
  • Forward every JavaScript errors (optional)
  • Forward JavaScript's console logs (optional)
  • Track real client IP address and user-agent (optional)
  • Automatic bulk posts (default to 500ms linger delay and 10 messages max per POST)
  • Small minified script < 2kb

Quick Start

Load and initialize logger

You simply have to include the minified script and initialize it with your write API key that can be found on your Logmatic.io platform.

    <title>Example to send logs to Logmatic.io</title>
    <script type="text/javascript" src="<path_to_tracekit>/tracekit/tracekit.js"></script> //OPTIONAL but provides better error handling
    <script type="text/javascript" src="<path_to_logmatic>/src/logmatic.min.js"></script>
      // Set your API key

      // OPTIONAL init methods
      // add some meta attributes in final JSON
      logmatic.setMetas({'userId': '1234'});
      // fwd any error using 'error' as JSON attr
      // fwd any console log using 'severity' as JSON attr
      // resolve client IP and copy it @ 'client.IP'
      // resolve client UA and copy it @ 'client.user-agent'
      // resolve URL and copy it @ 'url'
      // Default bulking setting - OPTIONAL modifications allowed
      logmatic.setBulkOptions({ lingerMs: 500, maxPostCount: 10, maxWaitingCount: -1 })

Using npm:

npm install --save tracekit@0.3.1 //OPTIONAL TraceKit is optional but it provides better error handling
npm install --save logmatic/logmatic-js#master
// commonjs
var TraceKit = require('tracekit'); //OPTIONAL but provides better error handling
var logmatic = require('logmatic-js');

// ES2015
// import TraceKit from 'tracekit'; //OPTIONAL but provides better error handling
// import logmatic from 'logmatic-js';

// Set your API key
// ...
// same as before

Handling of errors

You can handle errors by calling the setSendErrors initialization method. By default, logmatic-js catches all the errors from window.onerror.

However, we advise you to use TraceKit which is automatically recognized by logmatic-js and takes precedence over the former method. TraceKit gives you:

  • Stack traces when errors are properly fired
  • Resolves source maps for minified files
  • Resolves name of the method & add context

Please read their documentation for more details and options.

Log some events

Fire your own events

To log some events you simply there is simple an unique method called log(,). The message is a piece of text, the context is an object that you want to associate to the message.

logmatic.log('Button clicked', { name: 'My button name' });

To clearly explain what happens here, in this exact situation where everything is configured as above the API POSTs the following JSON content to Logmatic.io's API.:

  "severity": "info",
  "userId: "1234",
  "name": "My button name",
  "message": "Button clicked",
  "url": "...",
  "client": {
    "IP" : "109.30.xx.xxx",
    "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.130 Safari/537.36"

Automatic handling of errors

When setSendErrors init method is invoked with TraceKit enabled. Errors should be reported has this example below:

    "severity": "error",
    "client": {
      "IP": "109.30.xx.xxx",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.106 Safari/537.36"
    "message": "This is a fake error!!",
    "userId": "1234",
    "url": "../logmatic-js/test/test-client.html",
    "error": {
      "mode": "stack",
      "name": "Error",
      "message": "This is a fake error!!",
      "stack": [
          "args": [],
          "func": "bar",
          "line": 32,
          "column": 15,
          "context": {},
          "url": "../logmatic-js/test/test-client.html"
          "args": [],
          "func": "foo",
          "line": 28,
          "column": 9,
          "context": {},
          "url": "../logmatic-js/test/test-client.html"
        ... And more...

Try the test-client.html page

In test/, you'll find a test html page called test-client.html you can use to make some quick test. We encourage you to have a look at it as you'll be able to shoot a some log events in a few seconds.

Just don't forget to set your own API key.


You must call the init method to configure the logger:


There are one method for each level to send log events to Logmatic.io:

logmatic.log(<message>,<context>, <severity>);

You can also use all the following parameters using the right method:

Method Description Example
setMetas(object) add some meta attributes in final JSON .setMetas({ 'userId': '1234' })
addMeta(key, value) add some meta attributes in final JSON .addMeta("userEmail", "foo@example.com")
setSendErrors(exception_attr) fwd any error using exception_attr as JSON attr .setSendErrors('error');
setSendConsoleLogs(level_attr) fwd any console log using level_attr" as JSON attr .setSendConsoleLogs('level')
setIPTracking(ip_attr) resolve client IP and the "ip_attr" field to the event .setIPTracking('client.IP')
setUserAgentTracking(ua_attr) resolve client UA and the "ua_attr" field to the event .setUserAgentTracking('client.user-agent')
setURLTracking(url_attr) resolve URL and the "url_attr" field to the event .setURLTracking('url')
setBulkOptions({ lingerMs: duration_in_ms, maxPostCount: count, maxWaitingCount: count }) Options to configure the bulking behavior. Bulking limits the number of requests emitted. .setBulkOptions({ lingerMs: 500, maxPostCount: 10, maxWaitingCount: -1 })
lingerMs: A delay used to give a change to bulk a few line of logs together
maxPostCount: How many log lines should each post send at most (-1 no limit)
maxWaitingCount: How many log lines can be queued before dropping some (-1 no limit)


How to force a custom endpoint URL?

You can override the default URL with the logmatic.forceEndpoint('https://A_CUSTOM_URL') method. Notice, this method ignores the key set via the logmatic.init('API_KEY') method.