diff --git a/examples/test.js b/examples/test.js
index 3d8ecf02..6dca6ab3 100644
--- a/examples/test.js
+++ b/examples/test.js
@@ -12,7 +12,7 @@ FS.readFile(filepath, 'utf8', function(err, data) {
         throw err;
     }
 
-    svgo.optimize(data, function(result) {
+    svgo.optimize(data).then(function(result) {
 
         console.log(result);
 
diff --git a/lib/svgo.js b/lib/svgo.js
index c593023f..4c216790 100644
--- a/lib/svgo.js
+++ b/lib/svgo.js
@@ -17,44 +17,42 @@ var CONFIG = require('./svgo/config.js'),
     JS2SVG = require('./svgo/js2svg.js');
 
 var SVGO = module.exports = function(config) {
-
     this.config = CONFIG(config);
-
 };
 
-SVGO.prototype.optimize = function(svgstr, callback) {
-    if (this.config.error) return callback(this.config);
+SVGO.prototype.optimize = function(svgstr) {
+    return new Promise((resolve, reject) => {
+        if (this.config.error) {
+            reject(this.config.error);
+            return;
+        }
 
-    var _this = this,
-        config = this.config,
-        maxPassCount = config.multipass ? 10 : 1,
-        counter = 0,
-        prevResultSize = Number.POSITIVE_INFINITY,
-        optimizeOnceCallback = function(svgjs) {
+        var config = this.config,
+            maxPassCount = config.multipass ? 10 : 1,
+            counter = 0,
+            prevResultSize = Number.POSITIVE_INFINITY,
+            optimizeOnceCallback = (svgjs) => {
+                if (svgjs.error) {
+                    reject(svgjs.error);
+                    return;
+                }
 
-            if (svgjs.error) {
-                callback(svgjs);
-                return;
-            }
-
-            if (++counter < maxPassCount && svgjs.data.length < prevResultSize) {
-                prevResultSize = svgjs.data.length;
-                _this._optimizeOnce(svgjs.data, optimizeOnceCallback);
-            } else {
-                callback(svgjs);
-            }
-
-        };
-
-    _this._optimizeOnce(svgstr, optimizeOnceCallback);
+                if (++counter < maxPassCount && svgjs.data.length < prevResultSize) {
+                    prevResultSize = svgjs.data.length;
+                    this._optimizeOnce(svgjs.data, optimizeOnceCallback);
+                } else {
+                    resolve(svgjs);
+                }
+            };
 
+        this._optimizeOnce(svgstr, optimizeOnceCallback);
+    });
 };
 
 SVGO.prototype._optimizeOnce = function(svgstr, callback) {
     var config = this.config;
 
     SVG2JS(svgstr, function(svgjs) {
-
         if (svgjs.error) {
             callback(svgjs);
             return;
@@ -63,7 +61,6 @@ SVGO.prototype._optimizeOnce = function(svgstr, callback) {
         svgjs = PLUGINS(svgjs, config.plugins);
 
         callback(JS2SVG(svgjs, config.js2svg));
-
     });
 };
 
@@ -74,7 +71,5 @@ SVGO.prototype._optimizeOnce = function(svgstr, callback) {
  * @returns {JSAPI} content item
  */
 SVGO.prototype.createContentItem = function(data) {
-
     return new JSAPI(data);
-
 };
diff --git a/lib/svgo/coa.js b/lib/svgo/coa.js
index f58742e8..12177f5a 100644
--- a/lib/svgo/coa.js
+++ b/lib/svgo/coa.js
@@ -285,12 +285,7 @@ function optimizeFromString(svgstr, config, datauri, input, output) {
         outBytes,
         svgo = new SVGO(config);
 
-    svgo.optimize(svgstr, function(result) {
-        if (result.error) {
-            console.error(result.error);
-            return;
-        }
-
+    svgo.optimize(svgstr).then(function(result) {
         if (datauri) {
             result.data = encodeSVGDatauri(result.data, datauri);
         }
@@ -314,7 +309,7 @@ function optimizeFromString(svgstr, config, datauri, input, output) {
 
             saveFileAndPrintInfo(config, result.data, output, inBytes, outBytes, time);
         }
-    });
+    }, error => console.error(error));
 }
 
 function saveFileAndPrintInfo(config, data, path, inBytes, outBytes, time) {
@@ -439,12 +434,7 @@ function optimizeFolder(dir, config, output) {
                         inBytes = Buffer.byteLength(data, 'utf8'),
                         outBytes;
 
-                    svgo.optimize(data, function(result) {
-                        if (result.error) {
-                            console.error(result.error);
-                            return;
-                        }
-
+                    svgo.optimize(data).then(function(result) {
                         outBytes = Buffer.byteLength(result.data, 'utf8');
                         time = Date.now() - startTime;
 
@@ -482,7 +472,7 @@ function optimizeFolder(dir, config, output) {
                                 optimizeFile(files[i]);
                             }
                         }
-                    });
+                    }, error => console.error(error));
                 });
             }
             //move on to the next file
diff --git a/test/plugins/_index.js b/test/plugins/_index.js
index 508832f4..7ce3d52a 100644
--- a/test/plugins/_index.js
+++ b/test/plugins/_index.js
@@ -44,9 +44,8 @@ describe('plugins tests', function() {
                         js2svg  : { pretty: true }
                     });
 
-                    svgo.optimize(orig, function(result) {
-
-//FIXME: results.data has a '\n' at the end while it should not
+                    svgo.optimize(orig).then(function(result) {
+                        //FIXME: results.data has a '\n' at the end while it should not
                         normalize(result.data).should.be.equal(should);
                         done();
                     });
diff --git a/test/svgo/_index.js b/test/svgo/_index.js
index 1d218a21..053f3998 100644
--- a/test/svgo/_index.js
+++ b/test/svgo/_index.js
@@ -30,7 +30,7 @@ describe('indentation', function() {
                 js2svg  : { pretty: true, indent: 2 }
             });
 
-            svgo.optimize(orig, function(result) {
+            svgo.optimize(orig).then(function(result) {
                 normalize(result.data).should.be.equal(should);
                 done();
             });