diff --git a/karma-tests/karma.conf.js b/karma-tests/karma.conf.js
index b40190f2..af573a5a 100644
--- a/karma-tests/karma.conf.js
+++ b/karma-tests/karma.conf.js
@@ -1,8 +1,3 @@
-if (!process.env['SAUCE_USERNAME'] || !process.env['SAUCE_ACCESS_KEY']) {
-    console.error('Sauce Labs account details not set, skipping Karma tests');
-    process.exit(0);
-}
-
 var sauceLabsConfig = {
     testName: 'PyWB Client Tests',
 };
@@ -15,7 +10,7 @@ if (process.env.TRAVIS_JOB_NUMBER) {
 
 var WOMBAT_JS_PATH = 'pywb/static/wombat.js';
 
-var customLaunchers = {
+var sauceLaunchers = {
     sl_chrome: {
         base: 'SauceLabs',
         browserName: 'chrome',
@@ -26,18 +21,20 @@ var customLaunchers = {
         browserName: 'firefox',
     },
 
-/*  Safari and Edge are currently broken in
-    pywb.
-
-    See: https://github.com/ikreymer/pywb/issues/148 (Edge)
-         https://github.com/ikreymer/pywb/issues/147 (Safari)
-
     sl_safari: {
         base: 'SauceLabs',
         browserName: 'safari',
         platform: 'OS X 10.11',
         version: '9.0',
     },
+
+/*  Edge is currently broken in
+    pywb.
+
+    See: https://github.com/ikreymer/pywb/issues/148 (Edge)
+         https://github.com/ikreymer/pywb/issues/147 (Safari)
+
+
     sl_edge: {
         base: 'SauceLabs',
         browserName: 'MicrosoftEdge',
@@ -45,6 +42,24 @@ var customLaunchers = {
 */
 };
 
+var localLaunchers = {
+    localFirefox: {
+        base: 'Firefox',
+    },
+};
+
+var customLaunchers = {};
+
+if (process.env['SAUCE_USERNAME'] && process.env['SAUCE_ACCESS_KEY']) {
+    customLaunchers = sauceLaunchers;
+} else {
+    console.error('Sauce Labs account details not set, ' +
+                  'Karma tests will be run only against local browsers.' +
+                  'Set SAUCE_USERNAME and SAUCE_ACCESS_KEY environment variables to ' +
+                  'run tests against Sauce Labs browsers');
+    customLaunchers = localLaunchers;
+}
+
 module.exports = function(config) {
   config.set({
     basePath: '../',