diff --git a/README.md b/README.md
index 73766de..c40c470 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,7 @@ interface CountUpOptions {
   scrollSpyDelay?: number; // delay (ms) after target comes into view
   scrollSpyOnce?: boolean; // run only once
   onCompleteCallback?: () => any; // gets called when animation completes
+  onStartCallback?: () => any; // gets called when animation start
   plugin?: CountUpPlugin; // for alternate animations
 }
 ```
@@ -89,7 +90,13 @@ Pass options:
 const countUp = new CountUp('targetId', 5234, options);
 ```
 
-with optional callback:
+with optional start callback:
+
+```js
+const countUp = new CountUp('targetId', 5234, { onStartCallback: someMethod });
+```
+
+with optional complete callback:
 
 ```js
 const countUp = new CountUp('targetId', 5234, { onCompleteCallback: someMethod });
diff --git a/dist/countUp.d.ts b/dist/countUp.d.ts
index 6bc34f8..636e1b6 100644
--- a/dist/countUp.d.ts
+++ b/dist/countUp.d.ts
@@ -18,6 +18,7 @@ export interface CountUpOptions {
     scrollSpyDelay?: number;
     scrollSpyOnce?: boolean;
     onCompleteCallback?: () => any;
+    onStartCallback?: () => any;
     plugin?: CountUpPlugin;
 }
 export declare interface CountUpPlugin {
diff --git a/dist/countUp.js b/dist/countUp.js
index 6e0a52c..f9ebd1c 100644
--- a/dist/countUp.js
+++ b/dist/countUp.js
@@ -206,6 +206,9 @@ var CountUp = /** @class */ (function () {
         if (this.error) {
             return;
         }
+        if (this.options.onStartCallback) {
+            this.options.onStartCallback();
+        }
         if (callback) {
             this.options.onCompleteCallback = callback;
         }
diff --git a/dist/countUp.min.js b/dist/countUp.min.js
index 2bf68e8..aba2a75 100644
--- a/dist/countUp.min.js
+++ b/dist/countUp.min.js
@@ -1 +1 @@
-var t=function(){return t=Object.assign||function(t){for(var i,n=1,s=arguments.length;n<s;n++)for(var a in i=arguments[n])Object.prototype.hasOwnProperty.call(i,a)&&(t[a]=i[a]);return t},t.apply(this,arguments)},i=function(){function i(i,n,s){var a=this;this.endVal=n,this.options=s,this.version="2.7.1",this.defaults={startVal:0,decimalPlaces:0,duration:2,useEasing:!0,useGrouping:!0,useIndianSeparators:!1,smartEasingThreshold:999,smartEasingAmount:333,separator:",",decimal:".",prefix:"",suffix:"",enableScrollSpy:!1,scrollSpyDelay:200,scrollSpyOnce:!1},this.finalEndVal=null,this.useEasing=!0,this.countDown=!1,this.error="",this.startVal=0,this.paused=!0,this.once=!1,this.count=function(t){a.startTime||(a.startTime=t);var i=t-a.startTime;a.remaining=a.duration-i,a.useEasing?a.countDown?a.frameVal=a.startVal-a.easingFn(i,0,a.startVal-a.endVal,a.duration):a.frameVal=a.easingFn(i,a.startVal,a.endVal-a.startVal,a.duration):a.frameVal=a.startVal+(a.endVal-a.startVal)*(i/a.duration);var n=a.countDown?a.frameVal<a.endVal:a.frameVal>a.endVal;a.frameVal=n?a.endVal:a.frameVal,a.frameVal=Number(a.frameVal.toFixed(a.options.decimalPlaces)),a.printValue(a.frameVal),i<a.duration?a.rAF=requestAnimationFrame(a.count):null!==a.finalEndVal?a.update(a.finalEndVal):a.options.onCompleteCallback&&a.options.onCompleteCallback()},this.formatNumber=function(t){var i,n,s,e,o=t<0?"-":"";i=Math.abs(t).toFixed(a.options.decimalPlaces);var r=(i+="").split(".");if(n=r[0],s=r.length>1?a.options.decimal+r[1]:"",a.options.useGrouping){e="";for(var l=3,h=0,u=0,p=n.length;u<p;++u)a.options.useIndianSeparators&&4===u&&(l=2,h=1),0!==u&&h%l==0&&(e=a.options.separator+e),h++,e=n[p-u-1]+e;n=e}return a.options.numerals&&a.options.numerals.length&&(n=n.replace(/[0-9]/g,(function(t){return a.options.numerals[+t]})),s=s.replace(/[0-9]/g,(function(t){return a.options.numerals[+t]}))),o+a.options.prefix+n+s+a.options.suffix},this.easeOutExpo=function(t,i,n,s){return n*(1-Math.pow(2,-10*t/s))*1024/1023+i},this.options=t(t({},this.defaults),s),this.formattingFn=this.options.formattingFn?this.options.formattingFn:this.formatNumber,this.easingFn=this.options.easingFn?this.options.easingFn:this.easeOutExpo,this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.endVal=this.validateValue(n),this.options.decimalPlaces=Math.max(this.options.decimalPlaces),this.resetDuration(),this.options.separator=String(this.options.separator),this.useEasing=this.options.useEasing,""===this.options.separator&&(this.options.useGrouping=!1),this.el="string"==typeof i?document.getElementById(i):i,this.el?this.printValue(this.startVal):this.error="[CountUp] target is null or undefined","undefined"!=typeof window&&this.options.enableScrollSpy&&(this.error?console.error(this.error,i):(window.onScrollFns=window.onScrollFns||[],window.onScrollFns.push((function(){return a.handleScroll(a)})),window.onscroll=function(){window.onScrollFns.forEach((function(t){return t()}))},this.handleScroll(this)))}return i.prototype.handleScroll=function(t){if(t&&window&&!t.once){var i=window.innerHeight+window.scrollY,n=t.el.getBoundingClientRect(),s=n.top+window.pageYOffset,a=n.top+n.height+window.pageYOffset;a<i&&a>window.scrollY&&t.paused?(t.paused=!1,setTimeout((function(){return t.start()}),t.options.scrollSpyDelay),t.options.scrollSpyOnce&&(t.once=!0)):(window.scrollY>a||s>i)&&!t.paused&&t.reset()}},i.prototype.determineDirectionAndSmartEasing=function(){var t=this.finalEndVal?this.finalEndVal:this.endVal;this.countDown=this.startVal>t;var i=t-this.startVal;if(Math.abs(i)>this.options.smartEasingThreshold&&this.options.useEasing){this.finalEndVal=t;var n=this.countDown?1:-1;this.endVal=t+n*this.options.smartEasingAmount,this.duration=this.duration/2}else this.endVal=t,this.finalEndVal=null;null!==this.finalEndVal?this.useEasing=!1:this.useEasing=this.options.useEasing},i.prototype.start=function(t){this.error||(t&&(this.options.onCompleteCallback=t),this.duration>0?(this.determineDirectionAndSmartEasing(),this.paused=!1,this.rAF=requestAnimationFrame(this.count)):this.printValue(this.endVal))},i.prototype.pauseResume=function(){this.paused?(this.startTime=null,this.duration=this.remaining,this.startVal=this.frameVal,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count)):cancelAnimationFrame(this.rAF),this.paused=!this.paused},i.prototype.reset=function(){cancelAnimationFrame(this.rAF),this.paused=!0,this.resetDuration(),this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.printValue(this.startVal)},i.prototype.update=function(t){cancelAnimationFrame(this.rAF),this.startTime=null,this.endVal=this.validateValue(t),this.endVal!==this.frameVal&&(this.startVal=this.frameVal,null==this.finalEndVal&&this.resetDuration(),this.finalEndVal=null,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count))},i.prototype.printValue=function(t){var i;if(this.el){var n=this.formattingFn(t);if(null===(i=this.options.plugin)||void 0===i?void 0:i.render)this.options.plugin.render(this.el,n);else if("INPUT"===this.el.tagName)this.el.value=n;else"text"===this.el.tagName||"tspan"===this.el.tagName?this.el.textContent=n:this.el.innerHTML=n}},i.prototype.ensureNumber=function(t){return"number"==typeof t&&!isNaN(t)},i.prototype.validateValue=function(t){var i=Number(t);return this.ensureNumber(i)?i:(this.error="[CountUp] invalid start or end value: ".concat(t),null)},i.prototype.resetDuration=function(){this.startTime=null,this.duration=1e3*Number(this.options.duration),this.remaining=this.duration},i}();export{i as CountUp};
+var t=function(){return t=Object.assign||function(t){for(var i,n=1,s=arguments.length;n<s;n++)for(var a in i=arguments[n])Object.prototype.hasOwnProperty.call(i,a)&&(t[a]=i[a]);return t},t.apply(this,arguments)},i=function(){function i(i,n,s){var a=this;this.endVal=n,this.options=s,this.version="2.7.1",this.defaults={startVal:0,decimalPlaces:0,duration:2,useEasing:!0,useGrouping:!0,useIndianSeparators:!1,smartEasingThreshold:999,smartEasingAmount:333,separator:",",decimal:".",prefix:"",suffix:"",enableScrollSpy:!1,scrollSpyDelay:200,scrollSpyOnce:!1},this.finalEndVal=null,this.useEasing=!0,this.countDown=!1,this.error="",this.startVal=0,this.paused=!0,this.once=!1,this.count=function(t){a.startTime||(a.startTime=t);var i=t-a.startTime;a.remaining=a.duration-i,a.useEasing?a.countDown?a.frameVal=a.startVal-a.easingFn(i,0,a.startVal-a.endVal,a.duration):a.frameVal=a.easingFn(i,a.startVal,a.endVal-a.startVal,a.duration):a.frameVal=a.startVal+(a.endVal-a.startVal)*(i/a.duration);var n=a.countDown?a.frameVal<a.endVal:a.frameVal>a.endVal;a.frameVal=n?a.endVal:a.frameVal,a.frameVal=Number(a.frameVal.toFixed(a.options.decimalPlaces)),a.printValue(a.frameVal),i<a.duration?a.rAF=requestAnimationFrame(a.count):null!==a.finalEndVal?a.update(a.finalEndVal):a.options.onCompleteCallback&&a.options.onCompleteCallback()},this.formatNumber=function(t){var i,n,s,e,o=t<0?"-":"";i=Math.abs(t).toFixed(a.options.decimalPlaces);var r=(i+="").split(".");if(n=r[0],s=r.length>1?a.options.decimal+r[1]:"",a.options.useGrouping){e="";for(var l=3,h=0,u=0,p=n.length;u<p;++u)a.options.useIndianSeparators&&4===u&&(l=2,h=1),0!==u&&h%l==0&&(e=a.options.separator+e),h++,e=n[p-u-1]+e;n=e}return a.options.numerals&&a.options.numerals.length&&(n=n.replace(/[0-9]/g,(function(t){return a.options.numerals[+t]})),s=s.replace(/[0-9]/g,(function(t){return a.options.numerals[+t]}))),o+a.options.prefix+n+s+a.options.suffix},this.easeOutExpo=function(t,i,n,s){return n*(1-Math.pow(2,-10*t/s))*1024/1023+i},this.options=t(t({},this.defaults),s),this.formattingFn=this.options.formattingFn?this.options.formattingFn:this.formatNumber,this.easingFn=this.options.easingFn?this.options.easingFn:this.easeOutExpo,this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.endVal=this.validateValue(n),this.options.decimalPlaces=Math.max(this.options.decimalPlaces),this.resetDuration(),this.options.separator=String(this.options.separator),this.useEasing=this.options.useEasing,""===this.options.separator&&(this.options.useGrouping=!1),this.el="string"==typeof i?document.getElementById(i):i,this.el?this.printValue(this.startVal):this.error="[CountUp] target is null or undefined","undefined"!=typeof window&&this.options.enableScrollSpy&&(this.error?console.error(this.error,i):(window.onScrollFns=window.onScrollFns||[],window.onScrollFns.push((function(){return a.handleScroll(a)})),window.onscroll=function(){window.onScrollFns.forEach((function(t){return t()}))},this.handleScroll(this)))}return i.prototype.handleScroll=function(t){if(t&&window&&!t.once){var i=window.innerHeight+window.scrollY,n=t.el.getBoundingClientRect(),s=n.top+window.pageYOffset,a=n.top+n.height+window.pageYOffset;a<i&&a>window.scrollY&&t.paused?(t.paused=!1,setTimeout((function(){return t.start()}),t.options.scrollSpyDelay),t.options.scrollSpyOnce&&(t.once=!0)):(window.scrollY>a||s>i)&&!t.paused&&t.reset()}},i.prototype.determineDirectionAndSmartEasing=function(){var t=this.finalEndVal?this.finalEndVal:this.endVal;this.countDown=this.startVal>t;var i=t-this.startVal;if(Math.abs(i)>this.options.smartEasingThreshold&&this.options.useEasing){this.finalEndVal=t;var n=this.countDown?1:-1;this.endVal=t+n*this.options.smartEasingAmount,this.duration=this.duration/2}else this.endVal=t,this.finalEndVal=null;null!==this.finalEndVal?this.useEasing=!1:this.useEasing=this.options.useEasing},i.prototype.start=function(t){this.error||(this.options.onStartCallback&&this.options.onStartCallback(),t&&(this.options.onCompleteCallback=t),this.duration>0?(this.determineDirectionAndSmartEasing(),this.paused=!1,this.rAF=requestAnimationFrame(this.count)):this.printValue(this.endVal))},i.prototype.pauseResume=function(){this.paused?(this.startTime=null,this.duration=this.remaining,this.startVal=this.frameVal,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count)):cancelAnimationFrame(this.rAF),this.paused=!this.paused},i.prototype.reset=function(){cancelAnimationFrame(this.rAF),this.paused=!0,this.resetDuration(),this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.printValue(this.startVal)},i.prototype.update=function(t){cancelAnimationFrame(this.rAF),this.startTime=null,this.endVal=this.validateValue(t),this.endVal!==this.frameVal&&(this.startVal=this.frameVal,null==this.finalEndVal&&this.resetDuration(),this.finalEndVal=null,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count))},i.prototype.printValue=function(t){var i;if(this.el){var n=this.formattingFn(t);if(null===(i=this.options.plugin)||void 0===i?void 0:i.render)this.options.plugin.render(this.el,n);else if("INPUT"===this.el.tagName)this.el.value=n;else"text"===this.el.tagName||"tspan"===this.el.tagName?this.el.textContent=n:this.el.innerHTML=n}},i.prototype.ensureNumber=function(t){return"number"==typeof t&&!isNaN(t)},i.prototype.validateValue=function(t){var i=Number(t);return this.ensureNumber(i)?i:(this.error="[CountUp] invalid start or end value: ".concat(t),null)},i.prototype.resetDuration=function(){this.startTime=null,this.duration=1e3*Number(this.options.duration),this.remaining=this.duration},i}();export{i as CountUp};
diff --git a/dist/countUp.umd.js b/dist/countUp.umd.js
index 9c854c7..5a064cb 100644
--- a/dist/countUp.umd.js
+++ b/dist/countUp.umd.js
@@ -1 +1 @@
-!function(t,i){"object"==typeof exports&&"undefined"!=typeof module?i(exports):"function"==typeof define&&define.amd?define(["exports"],i):i((t="undefined"!=typeof globalThis?globalThis:t||self).countUp={})}(this,(function(t){"use strict";var i=function(){return i=Object.assign||function(t){for(var i,n=1,s=arguments.length;n<s;n++)for(var e in i=arguments[n])Object.prototype.hasOwnProperty.call(i,e)&&(t[e]=i[e]);return t},i.apply(this,arguments)},n=function(){function t(t,n,s){var e=this;this.endVal=n,this.options=s,this.version="2.7.1",this.defaults={startVal:0,decimalPlaces:0,duration:2,useEasing:!0,useGrouping:!0,useIndianSeparators:!1,smartEasingThreshold:999,smartEasingAmount:333,separator:",",decimal:".",prefix:"",suffix:"",enableScrollSpy:!1,scrollSpyDelay:200,scrollSpyOnce:!1},this.finalEndVal=null,this.useEasing=!0,this.countDown=!1,this.error="",this.startVal=0,this.paused=!0,this.once=!1,this.count=function(t){e.startTime||(e.startTime=t);var i=t-e.startTime;e.remaining=e.duration-i,e.useEasing?e.countDown?e.frameVal=e.startVal-e.easingFn(i,0,e.startVal-e.endVal,e.duration):e.frameVal=e.easingFn(i,e.startVal,e.endVal-e.startVal,e.duration):e.frameVal=e.startVal+(e.endVal-e.startVal)*(i/e.duration);var n=e.countDown?e.frameVal<e.endVal:e.frameVal>e.endVal;e.frameVal=n?e.endVal:e.frameVal,e.frameVal=Number(e.frameVal.toFixed(e.options.decimalPlaces)),e.printValue(e.frameVal),i<e.duration?e.rAF=requestAnimationFrame(e.count):null!==e.finalEndVal?e.update(e.finalEndVal):e.options.onCompleteCallback&&e.options.onCompleteCallback()},this.formatNumber=function(t){var i,n,s,a,o=t<0?"-":"";i=Math.abs(t).toFixed(e.options.decimalPlaces);var r=(i+="").split(".");if(n=r[0],s=r.length>1?e.options.decimal+r[1]:"",e.options.useGrouping){a="";for(var l=3,u=0,h=0,p=n.length;h<p;++h)e.options.useIndianSeparators&&4===h&&(l=2,u=1),0!==h&&u%l==0&&(a=e.options.separator+a),u++,a=n[p-h-1]+a;n=a}return e.options.numerals&&e.options.numerals.length&&(n=n.replace(/[0-9]/g,(function(t){return e.options.numerals[+t]})),s=s.replace(/[0-9]/g,(function(t){return e.options.numerals[+t]}))),o+e.options.prefix+n+s+e.options.suffix},this.easeOutExpo=function(t,i,n,s){return n*(1-Math.pow(2,-10*t/s))*1024/1023+i},this.options=i(i({},this.defaults),s),this.formattingFn=this.options.formattingFn?this.options.formattingFn:this.formatNumber,this.easingFn=this.options.easingFn?this.options.easingFn:this.easeOutExpo,this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.endVal=this.validateValue(n),this.options.decimalPlaces=Math.max(this.options.decimalPlaces),this.resetDuration(),this.options.separator=String(this.options.separator),this.useEasing=this.options.useEasing,""===this.options.separator&&(this.options.useGrouping=!1),this.el="string"==typeof t?document.getElementById(t):t,this.el?this.printValue(this.startVal):this.error="[CountUp] target is null or undefined","undefined"!=typeof window&&this.options.enableScrollSpy&&(this.error?console.error(this.error,t):(window.onScrollFns=window.onScrollFns||[],window.onScrollFns.push((function(){return e.handleScroll(e)})),window.onscroll=function(){window.onScrollFns.forEach((function(t){return t()}))},this.handleScroll(this)))}return t.prototype.handleScroll=function(t){if(t&&window&&!t.once){var i=window.innerHeight+window.scrollY,n=t.el.getBoundingClientRect(),s=n.top+window.pageYOffset,e=n.top+n.height+window.pageYOffset;e<i&&e>window.scrollY&&t.paused?(t.paused=!1,setTimeout((function(){return t.start()}),t.options.scrollSpyDelay),t.options.scrollSpyOnce&&(t.once=!0)):(window.scrollY>e||s>i)&&!t.paused&&t.reset()}},t.prototype.determineDirectionAndSmartEasing=function(){var t=this.finalEndVal?this.finalEndVal:this.endVal;this.countDown=this.startVal>t;var i=t-this.startVal;if(Math.abs(i)>this.options.smartEasingThreshold&&this.options.useEasing){this.finalEndVal=t;var n=this.countDown?1:-1;this.endVal=t+n*this.options.smartEasingAmount,this.duration=this.duration/2}else this.endVal=t,this.finalEndVal=null;null!==this.finalEndVal?this.useEasing=!1:this.useEasing=this.options.useEasing},t.prototype.start=function(t){this.error||(t&&(this.options.onCompleteCallback=t),this.duration>0?(this.determineDirectionAndSmartEasing(),this.paused=!1,this.rAF=requestAnimationFrame(this.count)):this.printValue(this.endVal))},t.prototype.pauseResume=function(){this.paused?(this.startTime=null,this.duration=this.remaining,this.startVal=this.frameVal,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count)):cancelAnimationFrame(this.rAF),this.paused=!this.paused},t.prototype.reset=function(){cancelAnimationFrame(this.rAF),this.paused=!0,this.resetDuration(),this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.printValue(this.startVal)},t.prototype.update=function(t){cancelAnimationFrame(this.rAF),this.startTime=null,this.endVal=this.validateValue(t),this.endVal!==this.frameVal&&(this.startVal=this.frameVal,null==this.finalEndVal&&this.resetDuration(),this.finalEndVal=null,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count))},t.prototype.printValue=function(t){var i;if(this.el){var n=this.formattingFn(t);if(null===(i=this.options.plugin)||void 0===i?void 0:i.render)this.options.plugin.render(this.el,n);else if("INPUT"===this.el.tagName)this.el.value=n;else"text"===this.el.tagName||"tspan"===this.el.tagName?this.el.textContent=n:this.el.innerHTML=n}},t.prototype.ensureNumber=function(t){return"number"==typeof t&&!isNaN(t)},t.prototype.validateValue=function(t){var i=Number(t);return this.ensureNumber(i)?i:(this.error="[CountUp] invalid start or end value: ".concat(t),null)},t.prototype.resetDuration=function(){this.startTime=null,this.duration=1e3*Number(this.options.duration),this.remaining=this.duration},t}();t.CountUp=n,Object.defineProperty(t,"__esModule",{value:!0})}));
+!function(t,i){"object"==typeof exports&&"undefined"!=typeof module?i(exports):"function"==typeof define&&define.amd?define(["exports"],i):i((t="undefined"!=typeof globalThis?globalThis:t||self).countUp={})}(this,(function(t){"use strict";var i=function(){return i=Object.assign||function(t){for(var i,n=1,s=arguments.length;n<s;n++)for(var e in i=arguments[n])Object.prototype.hasOwnProperty.call(i,e)&&(t[e]=i[e]);return t},i.apply(this,arguments)},n=function(){function t(t,n,s){var e=this;this.endVal=n,this.options=s,this.version="2.7.1",this.defaults={startVal:0,decimalPlaces:0,duration:2,useEasing:!0,useGrouping:!0,useIndianSeparators:!1,smartEasingThreshold:999,smartEasingAmount:333,separator:",",decimal:".",prefix:"",suffix:"",enableScrollSpy:!1,scrollSpyDelay:200,scrollSpyOnce:!1},this.finalEndVal=null,this.useEasing=!0,this.countDown=!1,this.error="",this.startVal=0,this.paused=!0,this.once=!1,this.count=function(t){e.startTime||(e.startTime=t);var i=t-e.startTime;e.remaining=e.duration-i,e.useEasing?e.countDown?e.frameVal=e.startVal-e.easingFn(i,0,e.startVal-e.endVal,e.duration):e.frameVal=e.easingFn(i,e.startVal,e.endVal-e.startVal,e.duration):e.frameVal=e.startVal+(e.endVal-e.startVal)*(i/e.duration);var n=e.countDown?e.frameVal<e.endVal:e.frameVal>e.endVal;e.frameVal=n?e.endVal:e.frameVal,e.frameVal=Number(e.frameVal.toFixed(e.options.decimalPlaces)),e.printValue(e.frameVal),i<e.duration?e.rAF=requestAnimationFrame(e.count):null!==e.finalEndVal?e.update(e.finalEndVal):e.options.onCompleteCallback&&e.options.onCompleteCallback()},this.formatNumber=function(t){var i,n,s,a,o=t<0?"-":"";i=Math.abs(t).toFixed(e.options.decimalPlaces);var r=(i+="").split(".");if(n=r[0],s=r.length>1?e.options.decimal+r[1]:"",e.options.useGrouping){a="";for(var l=3,u=0,h=0,p=n.length;h<p;++h)e.options.useIndianSeparators&&4===h&&(l=2,u=1),0!==h&&u%l==0&&(a=e.options.separator+a),u++,a=n[p-h-1]+a;n=a}return e.options.numerals&&e.options.numerals.length&&(n=n.replace(/[0-9]/g,(function(t){return e.options.numerals[+t]})),s=s.replace(/[0-9]/g,(function(t){return e.options.numerals[+t]}))),o+e.options.prefix+n+s+e.options.suffix},this.easeOutExpo=function(t,i,n,s){return n*(1-Math.pow(2,-10*t/s))*1024/1023+i},this.options=i(i({},this.defaults),s),this.formattingFn=this.options.formattingFn?this.options.formattingFn:this.formatNumber,this.easingFn=this.options.easingFn?this.options.easingFn:this.easeOutExpo,this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.endVal=this.validateValue(n),this.options.decimalPlaces=Math.max(this.options.decimalPlaces),this.resetDuration(),this.options.separator=String(this.options.separator),this.useEasing=this.options.useEasing,""===this.options.separator&&(this.options.useGrouping=!1),this.el="string"==typeof t?document.getElementById(t):t,this.el?this.printValue(this.startVal):this.error="[CountUp] target is null or undefined","undefined"!=typeof window&&this.options.enableScrollSpy&&(this.error?console.error(this.error,t):(window.onScrollFns=window.onScrollFns||[],window.onScrollFns.push((function(){return e.handleScroll(e)})),window.onscroll=function(){window.onScrollFns.forEach((function(t){return t()}))},this.handleScroll(this)))}return t.prototype.handleScroll=function(t){if(t&&window&&!t.once){var i=window.innerHeight+window.scrollY,n=t.el.getBoundingClientRect(),s=n.top+window.pageYOffset,e=n.top+n.height+window.pageYOffset;e<i&&e>window.scrollY&&t.paused?(t.paused=!1,setTimeout((function(){return t.start()}),t.options.scrollSpyDelay),t.options.scrollSpyOnce&&(t.once=!0)):(window.scrollY>e||s>i)&&!t.paused&&t.reset()}},t.prototype.determineDirectionAndSmartEasing=function(){var t=this.finalEndVal?this.finalEndVal:this.endVal;this.countDown=this.startVal>t;var i=t-this.startVal;if(Math.abs(i)>this.options.smartEasingThreshold&&this.options.useEasing){this.finalEndVal=t;var n=this.countDown?1:-1;this.endVal=t+n*this.options.smartEasingAmount,this.duration=this.duration/2}else this.endVal=t,this.finalEndVal=null;null!==this.finalEndVal?this.useEasing=!1:this.useEasing=this.options.useEasing},t.prototype.start=function(t){this.error||(this.options.onStartCallback&&this.options.onStartCallback(),t&&(this.options.onCompleteCallback=t),this.duration>0?(this.determineDirectionAndSmartEasing(),this.paused=!1,this.rAF=requestAnimationFrame(this.count)):this.printValue(this.endVal))},t.prototype.pauseResume=function(){this.paused?(this.startTime=null,this.duration=this.remaining,this.startVal=this.frameVal,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count)):cancelAnimationFrame(this.rAF),this.paused=!this.paused},t.prototype.reset=function(){cancelAnimationFrame(this.rAF),this.paused=!0,this.resetDuration(),this.startVal=this.validateValue(this.options.startVal),this.frameVal=this.startVal,this.printValue(this.startVal)},t.prototype.update=function(t){cancelAnimationFrame(this.rAF),this.startTime=null,this.endVal=this.validateValue(t),this.endVal!==this.frameVal&&(this.startVal=this.frameVal,null==this.finalEndVal&&this.resetDuration(),this.finalEndVal=null,this.determineDirectionAndSmartEasing(),this.rAF=requestAnimationFrame(this.count))},t.prototype.printValue=function(t){var i;if(this.el){var n=this.formattingFn(t);if(null===(i=this.options.plugin)||void 0===i?void 0:i.render)this.options.plugin.render(this.el,n);else if("INPUT"===this.el.tagName)this.el.value=n;else"text"===this.el.tagName||"tspan"===this.el.tagName?this.el.textContent=n:this.el.innerHTML=n}},t.prototype.ensureNumber=function(t){return"number"==typeof t&&!isNaN(t)},t.prototype.validateValue=function(t){var i=Number(t);return this.ensureNumber(i)?i:(this.error="[CountUp] invalid start or end value: ".concat(t),null)},t.prototype.resetDuration=function(){this.startTime=null,this.duration=1e3*Number(this.options.duration),this.remaining=this.duration},t}();t.CountUp=n,Object.defineProperty(t,"__esModule",{value:!0})}));
diff --git a/src/countUp.ts b/src/countUp.ts
index 3163a9b..aa1d5e8 100644
--- a/src/countUp.ts
+++ b/src/countUp.ts
@@ -19,6 +19,7 @@ export interface CountUpOptions { // (default)
   scrollSpyDelay?: number; // delay (ms) after target comes into view
   scrollSpyOnce?: boolean; // run only once
   onCompleteCallback?: () => any; // gets called when animation completes
+  onStartCallback?: () => any; // gets called when animation starts
   plugin?: CountUpPlugin; // for alternate animations
 }
 
@@ -163,6 +164,9 @@ export class CountUp {
     if (this.error) {
       return;
     }
+    if(this.options.onStartCallback) {
+      this.options.onStartCallback();
+    }
     if (callback) {
       this.options.onCompleteCallback = callback;
     }