When Power Query combines data from separate locations, its Data Mashup Engine builds isolated security boundaries to prevent data leaks. However, this isolation often slows down data refreshes or triggers formula firewall errors. Fast Combine instructs Power Query to skip these isolation checks, combining queries directly without evaluating cross-source security boundaries.
Quick Answer:
To configure Fast Combine in Excel, open the Data tab, click Get Data > Query Options. Under Current Workbook, select Privacy, click Ignore the Privacy levels and potentially improve performance, and select OK. To apply this setting across all workbooks on your system, select the same option under the Global > Privacy menu.
What Fast Combine Actually Does
Under standard operation, the Power Query Mashup Engine partitions every query according to its data source and assigned privacy level (Public, Organizational, or Private). Before evaluating any step that joins, appends, or passes variables between queries, the engine analyzes the execution graph:
- It checks whether a step sends data from a more private container to a less private container.
- It blocks server-side query folding if parameter values originate from an external or local file.
- It buffers tables in local memory to ensure untrusted code does not execute against secure systems.
While these safeguards protect sensitive corporate data, they introduce severe processing overhead. For workbooks that consolidate internal spreadsheets, trusted enterprise databases, and local text files, this extra layer of validation is often redundant.
Enabling Fast Combine turns off this partition analysis. The engine treats all sources within the workbook as a single execution space, enabling parallel requests and direct data merges without intermediate firewall validation.
Step-by-Step Configuration
Depending on your workflow, you can enable Fast Combine for a single file or across your entire Excel application.
Method 1: Enable for the Current Workbook (Recommended)
This approach prevents security compromises if you later open unvetted files from outside sources.
- Open your Excel workbook.
- Go to the Data tab on the ribbon.
- Click Get Data and select Query Options.
- In the left panel, find the Current Workbook group and click Privacy.
- Select the third option: Ignore the Privacy levels and potentially improve performance.
- Click OK, then refresh your queries.
Method 2: Enable Globally Across All Workbooks
Use this option if you only build internal reporting models and want to stop privacy interruptions permanently across all files.
- Go to Data > Get Data > Query Options.
- In the left panel, under the Global heading, select Privacy.
- Select Always ignore Privacy Level settings.
- Click OK.
Verifying That Fast Combine Is Working
After enabling Fast Combine, verify that your queries are operating without security partitions:
- Elimination of Prompts: You will no longer see the
"Information is needed about data privacy"dialog during refreshes. (If you still encounter this dialog on legacy files, review “Information is needed about data privacy” popup: How to stop it permanently). - Resolution of Firewall Errors: Queries that previously stopped on
Formula.Firewallhalts will now run directly. For deeper context on what triggered the block originally, see Formula.Firewall: Data privacy settings prevent combining sources. - Faster Execution: Multi-source merges will begin loading simultaneously rather than stalling during initial step evaluation.
Troubleshooting: When Fast Combine Fails to Resolve Errors
If you enabled Fast Combine but your queries still fail or freeze during refresh:
1. Stale Cached Data Source Permissions
If a specific connection within your workbook has an invalid or corrupted credential token, the query engine halts before Fast Combine logic even applies.
- Go to Data > Get Data > Data Source Settings.
- Check Global permissions for duplicate paths or expired log-ins.
- Select any problematic connections and click Clear Permissions.
- Detailed cleanup procedures are covered in Managing Data Source Settings: How to clear and reset Global Permissions.
2. Native Query Blocks
Fast Combine bypasses privacy boundary checks, but it does not automatically permit unapproved native database queries. If your query incorporates raw SQL or custom database scripts, Excel’s native query security sandbox may still block execution. See Troubleshooting Native Database Queries and the “Permission Denied” error to adjust script approval rules.
3. Organizational Policy Overrides
In some enterprise environments, Microsoft 365 Group Policies (GPO) or tenant-level admin settings lock the Privacy settings. If the options under Query Options > Privacy appear greyed out, your workstation is enforced by centralized administrator rules, and privacy levels must instead be reconciled manually using How to fix Privacy Level Mismatches: Public vs. Organizational vs. Private.
Security Risk Considerations
Bypassing privacy overhead is safe for closed, trusted environments, but it removes safeguards against unauthorized data transmission. If you build queries that pull from sensitive customer files while querying third-party internet endpoints, Fast Combine allows data from the private source to be included in outbound web URLs or API headers.
Before deploying workbooks with Fast Combine active across multi-tenant teams, read Understanding the “Ignore Privacy Levels” setting: Risks and Rewards to evaluate where strict isolation should remain enabled.