What is Generate Thumbnails as User in Tableau?

Ever noticed those small preview images for your views and dashboards when browsing content on Tableau Server or Tableau Cloud? Those are thumbnails, and a specific permission called "Generate Thumbnails as User" dictates exactly what they show. This article will explain what this setting does, why it matters for both user experience and data security, and how to configure it correctly for your needs.

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What Exactly Are Thumbnails in Tableau?

Before diving into the permission itself, let's start with the basics. In Tableau, thumbnails are the small, static image previews of your vizzes and dashboards. You see them when you browse through projects, look at lists of workbooks, or search for content on Tableau Server or Tableau Cloud.

Their purpose is simple: to give you a quick visual glimpse of the content without having to open it. Think of them like book covers in a digital library. They help you quickly identify the dashboard you're looking for, making navigation faster and more intuitive. Instead of reading dozens of workbook names, you can often recognize a familiar chart or layout instantly.

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Decoding the "Generate Thumbnails as User" Permission

This is where things get interesting. The "Generate Thumbnails as User" permission is a specific capability you can assign to users or groups in Tableau. It controls how these thumbnail images are created, especially when your dashboards use data security rules like Row-Level Security (RLS).

At its core, this one setting answers a critical question: "Should the thumbnail preview look the same for everyone, or should it reflect the specific data that each individual user is allowed to see?"

Let's break down the two outcomes.

When the Permission is "Allowed"

If a user has this permission set to "Allowed," Tableau will generate a unique, personalized thumbnail for them. This thumbnail is rendered based on the data that this specific user has access to.

• What it means: The thumbnail preview accurately reflects the filtered view the user will see when they open the actual dashboard.
• Relatable Example: Imagine a master sales dashboard that shows performance data for a team of 10 sales reps. Each rep can only see their own opportunities and sales numbers (this is a classic use case for Row-Level Security).

In this scenario, the thumbnail is a true, personalized preview. It confirms to Mary that she's looking at her own data and gives John his broader team overview, all before anyone even clicks on the dashboard.

When the Permission is "Denied"

If a user has this permission set to "Denied," Tableau does not generate a personalized thumbnail for them. Instead, they see a single, generic thumbnail that was generated by one user - typically, the person who published the workbook.

• What it means: Everyone sees the exact same thumbnail image, regardless of what their individual data permissions are.
• Relatable Example: Let's use the same sales dashboard. The dashboard was published by the Tableau administrator.

When Mary clicks to open the dashboard, the view will update to show only her data. The RLS still works inside the viz, but the preview thumbnail outside of it is generic and may not reflect what she'll actually see. This can sometimes cause confusion if the preview looks drastically different from the real dashboard view.

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Why This Permission Matters: Balancing Experience and Performance

Choosing whether to allow or deny this permission involves a trade-off. You're generally balancing user experience and security precision against server performance and resource load. There isn't a single "right" answer, it depends entirely on your dashboard's purpose and your organization's priorities.

Three Reasons to Allow "Generate Thumbnails As User"

1. Better User Experience: Personalized thumbnails are far more intuitive. Users see a preview that matches what they will get when they open the dashboard, which reduces confusion and builds trust in the content. John, the manager, can instantly tell from the preview that he's looking at the team summary.
2. Maintains Security and RLS Context: This is the big one. Allowing it ensures that your thumbnail images respect your data security rules. If the purpose of your RLS is to strictly partition data between users, then your previews should reflect that partitioning. Showing a generic thumbnail with someone else's data, or all data, could be misleading at best and a potential information leak at worst.
3. Confirms Correct Filtering: For users, seeing a familiar, filtered view in the thumbnail acts as a confirmation that their permissions are working correctly before they even open the viz.

Three Reasons You Might Deny "Generate Thumbnails As User"

1. Reduced Server Load: This is the primary reason to deny the permission. Generating and serving a custom thumbnail for every single user looking at a dashboard is more work for your Tableau Server or Cloud site. If you have thousands of users viewing hundreds of dashboards, the processing load can add up and potentially slow down page load times. A single, cached, generic thumbnail is much more efficient.
2. Simplified Caching: When everyone sees the same thumbnail, Tableau can cache that one image and serve it quickly to all users. When every user gets a different thumbnail, caching becomes far less effective.
3. No RLS Needed: If a dashboard doesn't have any Row-Level Security and is meant to look the same for all viewers (e.g., a high-level company overview or public-facing information), there is absolutely no benefit to generating unique thumbnails. Denying the permission here is a simple optimization.

How to Set This Permission in Tableau

Finding this setting is straightforward once you know where to look. You can set permissions at the project level (all content in that project inherits the permissions) or on an individual piece of content like a workbook.

Here’s the step-by-step process:

1. Navigate to the Project folder or the specific Workbook on your Tableau Server or Tableau Cloud site.
2. Click the three-dots icon (... ) to open the Actions menu.
3. Select Permissions from the dropdown menu.
4. This will open the Permissions dialog window. You'll see a list of existing permission rules for different users and groups.
5. Click + Add Group/User Rule to create a new rule or click on an existing rule to edit it.
6. In the permission templates dropdown, you can see if the preset roles (like Viewer or Explorer) have this capability. For more granular control, click to expand the permissions list.
7. Scroll down through the list of capabilities. Under the "Workbooks" section, you'll find the option for Generate Thumbnails as User.
8. Set it to Allowed or Denied as needed, then click Save.

**Quick Tip:** Remember that Tableau permissions can be nuanced. A user's "effective permissions" are a combination of their explicit user permissions, the permissions of all groups they belong to, and the permissions of the content they are accessing. It's always a good idea to double-check who has access to what, especially in highly secure environments.

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Best Practices for Common Scenarios

So, when should you lean one way versus the other? Here are some common scenarios and a recommended best practice for each.

Scenario 1: Highly Sensitive Financial and HR Dashboards

• Dashboard Type: Executive salary dashboards, individual performance compensation reports, or regional budget dashboards where managers can only see their department's data.
• Recommendation: Allow "Generate Thumbnails as User."
• Why: Data confidentiality is paramount. You never want a manager accidentally seeing a thumbnail that includes another department's sensitive salary data. The preview must respect the RLS to maintain the integrity of your security model. The slight performance hit is a worthy trade-off for security and accuracy.

Scenario 2: Public or Company-Wide General Information

• Dashboard Type: A general website traffic summary, a directory of company office locations, or an embedded dashboard on a public website. The data looks the same for every single viewer.
• Recommendation: Deny "Generate Thumbnails as User."
• Why: There is no RLS and therefore no need for personalized previews. Forcing the server to generate a unique thumbnail for each user is pure overhead. Save the computing resources and simplify caching by denying this permission.

Scenario 3: A Large E-Commerce Platform with a Mix of Users

• Dashboard Type: Multiple sales and operations dashboards accessed by thousands of internal employees and hundreds of external vendors. Some vendors can only see their own product sales (RLS). Some internal users see a wider scope of data.
• Recommendation: Use a hybrid approach starting with a performance-first default.
• Why: This approach gives you the best of both worlds. You gain performance benefits across the majority of your content while applying the more resource-intensive, personalized previews only where they are functionally necessary.

Final Thoughts

The "Generate Thumbnails as User" permission in Tableau is a subtle but powerful tool for fine-tuning your BI environment. It allows you to strike a deliberate balance between offering a highly personalized, secure user experience and maintaining optimal server performance. By understanding how it works and applying it thoughtfully based on your content's needs, you can build a more efficient and intuitive reporting platform for all your users.

Of course, managing the nuances of BI tool permissions and configurations is just one part of the data puzzle. We created Graphed because we believe getting insights shouldn't require you to become an expert in server settings. Instead of worrying about thumbnail generation, RLS setup, and performance tuning inside a complex platform, we help you ask questions directly in natural language. Connect your data sources once, and our AI analyst builds the live, personalized dashboards you need in seconds, making data accessible to everyone on your team without the steep learning curve.