diff --git a/src/__tests__/utils.js b/src/__tests__/utils.js
index a3ca73dfd..b60b98b70 100644
--- a/src/__tests__/utils.js
+++ b/src/__tests__/utils.js
@@ -5,7 +5,13 @@
  * currently not supported in the browser lib).
  */
 
-import { _copyAndTruncateStrings, _info, loadScript } from '../utils'
+import { _copyAndTruncateStrings, _info, _isBlockedUA, DEFAULT_BLOCKED_UA_STRS, loadScript } from '../utils'
+
+function userAgentFor(botString) {
+    const randOne = (Math.random() + 1).toString(36).substring(7)
+    const randTwo = (Math.random() + 1).toString(36).substring(7)
+    return `Mozilla/5.0 (compatible; ${botString}/${randOne}; +http://a.com/bot/${randTwo})`
+}
 
 describe(`utils.js`, () => {
     it('should have $host and $pathname in properties', () => {
@@ -208,4 +214,15 @@ describe('loadScript', () => {
         new_script.onerror('uh-oh')
         expect(callback).toHaveBeenCalledWith('uh-oh')
     })
+
+    describe('user agent blocking', () => {
+        it.each(DEFAULT_BLOCKED_UA_STRS.concat('testington'))(
+            'blocks a bot based on the user agent %s',
+            (botString) => {
+                const randomisedUserAgent = userAgentFor(botString)
+
+                expect(_isBlockedUA(randomisedUserAgent, ['testington'])).toBe(true)
+            }
+        )
+    })
 })
diff --git a/src/utils.ts b/src/utils.ts
index f4a0a2772..e98058d73 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -461,7 +461,7 @@ export const _utf8Encode = function (string: string): string {
     return utftext
 }
 
-const BLOCKED_UA_STRS = [
+export const DEFAULT_BLOCKED_UA_STRS = [
     'ahrefsbot',
     'applebot',
     'baiduspider',
@@ -503,18 +503,13 @@ const BLOCKED_UA_STRS = [
     'storebot-google',
 ]
 
-let botRegex: RegExp | null = null
 // _.isBlockedUA()
 // This is to block various web spiders from executing our JS and
 // sending false capturing data
 export const _isBlockedUA = function (ua: string, customBlockedUserAgents: string[]): boolean {
-    if (botRegex === null) {
-        // convert BLOCKED_UA_STRS to a regex like bot.php|hubspot|crawler|prerender etc.:
-        const joinedBots = BLOCKED_UA_STRS.concat(customBlockedUserAgents).join('|')
-        botRegex = new RegExp(joinedBots, 'i')
-    }
-
-    return !botRegex.test(ua)
+    return DEFAULT_BLOCKED_UA_STRS.concat(customBlockedUserAgents).some((blockedUA) => {
+        return ua.includes(blockedUA)
+    })
 }
 
 /**