diff --git a/lib/init.js b/lib/init.js
index e9d285b0..45fd60d2 100644
--- a/lib/init.js
+++ b/lib/init.js
@@ -15,7 +15,7 @@ const pickChainUrl = require('./pick-chain-url');
 
 /**
  * @param {string} apiKey - (optional) Your Etherscan APIkey
- * @param {string} chain - (optional) Other chain keys [ropsten, rinkeby, kovan]
+ * @param {string} chain - (optional) Other chain keys [ropsten, rinkeby, kovan] or the explorer api url
  * @param {number} timeout - (optional) Timeout in milliseconds for requests, default 10000
  * @param {object} client - optional axios client instance
  */
diff --git a/lib/pick-chain-url.js b/lib/pick-chain-url.js
index 176c3b75..af200ade 100644
--- a/lib/pick-chain-url.js
+++ b/lib/pick-chain-url.js
@@ -14,15 +14,20 @@ const OTHER_API_URL_MAP = {
 
 /**
  * gets  the correct urls of the backend 
- * @param {string} chain 
+ * @param {string} chainOrUrl
  * @returns Url of backend
  */
-function pickChainUrl(chain) {
-    if (!chain || !OTHER_API_URL_MAP[chain]) {
-      return MAIN_API_URL;
+function pickChainUrl(chainOrUrl) {
+    if (!chainOrUrl) {
+        return MAIN_API_URL;
     }
-    return OTHER_API_URL_MAP[chain];
+
+    if (!OTHER_API_URL_MAP[chainOrUrl]) {
+        return chainOrUrl;
+    }
+
+    return OTHER_API_URL_MAP[chainOrUrl];
 }
 
 
-  module.exports = pickChainUrl;
+module.exports = pickChainUrl;