Today, HDC signs all files contained in a submitted driver package (.cab/HLKx), regardless of whether they are referenced by the INF.
With the upcoming change, any files in a submitted package that are not referenced by the INF will be returned unsigned.
Impact on Windows Update Publication
Driver packages published to Windows Update will include only INF‑referenced files.
This means customers receiving driver updates will install packages that contain only the files required by the INF.
To help minimize disruption:
- Starting February 23, HDC will enable this policy in “On with Logging Only” mode.
- Submissions will be processed normally.
- Partners will be able to see whether this change affects their packages through either HDC submissions or the HLK:
- HDC - The signing logs provided in HDC submissions are available in both the UI and API. Note: if the submission does not contain any unreferenced files, the logs will not be present.
- HLK - February 2026 HLK refresh release will present a warning when the driver package is added to the submission package if the driver package contains files that are not referenced in an INF.
- Microsoft will collect partner feedback through bug reports and direct engagement. This will allow us to identify any scenarios that require special handling or further consideration.
- After feedback is reviewed, Microsoft will announce the date when the policy changes to “On and Enforced” mode where any files in a submitted package that are not referenced by the INF will be returned unsigned.
Why this change matters
This change improves package integrity and aligns WU deliveries with the set of files your INF declares, reducing the risk of unsigned and unreferenced artifacts in distributed driver bundles.
Who is impacted
- OEMs, IHVs, and driver developers who submit packages to HDC for signing.
- Partners who include helper tools, debug utilities, or extra artifacts in packages without INF references.
What you need to do (checklist)
- Audit your packages for unreferenced files (files not listed in INF sections such as SourceDisksFiles, CatalogFile, or other driver package manifest references. More information can be found here: INF SourceDisksFiles Section - Windows drivers | Microsoft Learn and to validate whether there are unreferenced files please pick up the latest HLK here: Windows Hardware Lab Kit | Microsoft Learn
- Ensure the driver package only contains the files needed for the functioning of the driver package
- Validate your package with the latest HLK validation tools before submitting to HDC.
- Note: The February 2026 refresh of the HLK will showcase a warning at package creation time if unreferenced files are found in the driver. See What's new in the Hardware Lab Kit | Microsoft Learn for more information.
- Update automation if you have it to create submissions or process signed packages to avoid adding unreferenced files.
Important operational detail: When enforcement starts, HDC will continue to accept packages that contain unreferenced files; those unreferenced files will simply be returned unsigned. This initial implementation does not reject submissions for unreferenced files; stricter enforcement may be considered later.
Timeline
- Start enforcement of “On with Logging Only” mode: February 23rd.
- Update of enforcement of “On and Enforced” mode: To be announced – when any files in a submitted package that are not referenced by an INF will be returned unsigned.
How this works in practice
- Output you receive from HDC: The returned package may contain unsigned unreferenced files alongside signed INF referenced files. Signed driver bundles published to WU will no longer contain files unreferenced in an inf.
Links & resources
- Get a submission - Windows drivers | Microsoft Learn
- What's new in the Hardware Lab Kit | Microsoft Learn
- Partner Center doc & support: Support for Partner Center Dashboard - Windows drivers | Microsoft Learn
Frequently asked Questions
Q1: What is an “unreferenced file”?
A: An unreferenced file is any file in your submitted package that is not listed in an INF. More information can be found here: INF SourceDisksFiles Section - Windows drivers | Microsoft Learn. Such files will not receive embedded signatures in this phase. Note: If adding files to an INF ensure that they are referenced correctly, if they are not then they will be treated as an unreferenced file. INF Verif in the WDK can assist in ensuring the files are referenced correctly.
Q2: What happens if I submit a package with unreferenced files?
A: During the “On with Logging Only” mode, submissions will be processed normally, and partners can see whether this change will affect them. During the “On and Enforced” mode, HDC will return the driver package; only the INF referenced files will be signed. The unreferenced files will be returned unsigned. Driver packages published to Windows Update will include only INF‑referenced files.
Q3: Will my package be rejected?
A: Not in the initial phase. We may move to stricter enforcement later (e.g., rejecting packages that contain unreferenced files). We’ll publish dates and guidance well in advance.
Q4: What will be published to Windows Update?
A: Only INF referenced files will be included in the signed driver bundles that are published to Windows Update.
Q5: Do nested CAB files get embedded signing?
A: No. HDC does not perform embedded signing on nested CAB files; those components are protected by catalog signing and are out of scope for this change.
Q6: I have runtime dependencies that aren’t in the INF (e.g., firmware blobs, config files, user mode DLLs). What should I do?
A: If such a file is needed at runtime, it must be referenced in the INF to be signed and delivered via WU. Otherwise, it will be returned unsigned and will not be included in WU bundles. Plan to add appropriate INF references or maintain your own distribution for those artifacts.
Q7: How can I check for unreferenced files?
A: Partners will be able to see whether this change affects their packages through either HDC submissions or using the HLK:
- HDC - The signing logs provided in HDC submissions are available in both the UI and API. Note: if the submission does not contain any unreferenced files, the logs will not be present. Examples:
- HDC On and Logging message:
- Warning: This submission contains one or more files that are not referenced by any INF in the submitted driver package. These files have been signed and published; however, in a future update, files not referenced by an INF will no longer be eligible for signing or publishing. For additional information on unreferenced files, see the documentation
- HDC On and Enforced message:
- Attention: This submission contains one or more files that are not referenced by any INF in the submitted driver package. Files not referenced by an INF are not eligible for signing or publishing. For additional information on unreferenced files, see the documentation.
- HDC On and Logging message:
Note: The messaging above will be seen at the submission level, though it is possible that the initial submission package does not contain unreferenced files, but the derived package contains additional files which are unreferenced. In this case, the partner verbiage would be displayed at the derived submission level, and not at the top-level submission.
- HLK - February 2026 HLK refresh release will present a warning when the driver package is added to the submission package if there are unreferenced files included in the driver package.
Q8: How are symbol files handled since they are not referenced by an INF?
A: Symbol files today are not included in the signed driver package that is returned. This behavior is not changing, and symbol files do not need to be referenced in an INF. Including symbols with your driver package is highly recommended.
Q9: Will HDC fail submissions that contain unreferenced files?
A: Not in this phase. Submissions will still be accepted; unreferenced files will be returned unsigned. Stricter enforcement may be considered later after partners have time to adapt.
Q10: How can I tell what files are signed by Microsoft?
A: How to validate the Microsoft signature - Windows drivers | Microsoft Learn
Q11: Where can I get help?
A: If you need direct assistance, open a Partner Center support case and reference this policy change. Support for Partner Center Dashboard - Windows drivers | Microsoft Learn
Microsoft