Browser Monitors: How to enable 3rd Party cookies

[HannahM]

Summary

Since Chromium version 122, third-party cookies are blocked by default. This can cause Dynatrace Synthetic Browser Monitors to behave differently from real-user browsing sessions, resulting in pages failing to load, authentication issues, or incomplete transactions.

This article explains how to identify when blocked third-party cookies are causing Browser Monitor failures and how to enable third-party cookies for local playback and Private Synthetic Locations.

• Summary
• Problem
• Resolution
• Local playback
• Option 1: Disable Third-Party Cookie Blocking in Chrome Incognito
• Option 2: Allow Third-Party Cookies for Specific Sites
• Private Synthetic Locations
• Cluster Version 315 and Later
• Cluster Versions Prior to 315
• Step 1: Identify Existing Disabled Features
• Step 2: Apply the Configuration
• What's next
• Related reading

Problem

A Dynatrace Browser Monitor doesn't load a website as expected, even though the site works correctly when accessed manually.

Browser Monitor screenshots may show incomplete rendering or failure messages caused by required third-party cookies being blocked.

Because Chromium 122 blocks third-party cookies by default, websites that rely on them may not function correctly during Synthetic execution unless this behavior is explicitly disabled.

Resolution

Local playback

There are two supported approaches.

Option 1: Disable Third-Party Cookie Blocking in Chrome Incognito

1. Open an Incognito window.
2. Navigate to Chrome privacy settings.
3. Disable Block third-party cookies.
   
   
   This setting persists for future local playbacks.

Option 2: Allow Third-Party Cookies for Specific Sites

1. Open Chrome.
2. Navigate to chrome://settings/cookies
3. Add the affected website domain to the list of sites allowed to use third-party cookies.
   

Private Synthetic Locations

To allow third-party cookies in Private Synthetic Locations, disable Chromium's third-party cookie protection feature by using the startup parameter:

--disable-features=TrackingProtection3pcd

 

Cluster Version 315 and Later

No configuration changes are required.

Starting with Cluster version 315, the TrackingProtection3pcd Chrome feature is disabled by default.

Important

If you previously customized the Browser Monitor configuration using the procedure for older cluster versions, review and remove the custom configuration where appropriate so that the default feature list can be used.

Cluster Versions Prior to 315

Step 1: Identify Existing Disabled Features

1. Locate the vuc-browser.log for the Private Location
2. Search for --disable-features= and copy the whole value.
   For example, 
   

   --disable-features=OptimizationGuideModelDownloading,OptimizationHintsFetching,OptimizationTargetPrediction,OptimizationHints,TFLiteLanguageDetectionEnabled,HttpsUpgrades,HttpsFirstBalancedMode

   So, the value is

   OptimizationGuideModelDownloading,OptimizationHintsFetching,OptimizationTargetPrediction,OptimizationHints,TFLiteLanguageDetectionEnabled,HttpsUpgrades,HttpsFirstBalancedMode

3. Append ,TrackingProtection3pcd to the list of values. 
   

   OptimizationGuideModelDownloading,OptimizationHintsFetching,OptimizationTargetPrediction,OptimizationHints,TFLiteLanguageDetectionEnabled,HttpsUpgrades,HttpsFirstBalancedMode,TrackingProtection3pcd

Step 2: Apply the Configuration

This feature can be disabled for all monitors running on the ActiveGate, or for a single monitor. 

Note: These changes persist on update, so if new features are disabled by default, you may need to update your snippet.

Option A: All Browser Monitors on the ActiveGate

1. On the ActiveGate, open the user.properties file

1. • C:\\ProgramData\\dynatrace\\synthetic\\config\\user.properties on Windows
   • /var/lib/dynatrace/synthetic/config/user.properties on Linux
2. Add the following line
   

   com.ruxit.vuc.poolConfig.playerConfig.toRemoveStartupParams=--disable-features​

3. Them on the following line, add the --disable-features snippet created earlier after com.ruxit.vuc.poolConfig.playerConfig.additionalStartupParams=--disable-features. For example
    

   com.ruxit.vuc.poolConfig.playerConfig.toRemoveStartupParams=--disable-features​
   com.ruxit.vuc.poolConfig.playerConfig.additionalStartupParams=--disable-features=OptimizationGuideModelDownloading,OptimizationHintsFetching,OptimizationTargetPrediction,OptimizationHints,TFLiteLanguageDetectionEnabled,HttpsUpgrades,HttpsFirstBalancedMode,TrackingProtection3pcd​

Option B: Single Browser Monitor

1. Open Monitor → Settings → Recorded Clickpath.
2. Switch to Script mode.
3. Add the following snippet into the configuration section and update the value to be the snippet created earlier
   

   ,
   "experimentalProperties": [{ 
               "name": "disable-features", 
               "value": "OptimizationGuideModelDownloading,OptimizationHintsFetching,OptimizationTargetPrediction,OptimizationHints,TFLiteLanguageDetectionEnabled,HttpsUpgrades,HttpsFirstBalancedMode,TrackingProtection3pcd​" 
           }]​

   
   
4. Save your changes

Resize issue view side panel.

What's next

If this does not resolve the issue, please open a support ticket and provide

• a link to the affected monitor
• mention this article and any other troubleshooting steps taken

Related reading

📖  Script mode for Browser monitor configuration
📖  Synthetic Troubleshooting Map

📖  Synthetic Browser Monitor Error Codes