How can I read / write Alternate Data Streams on a Google Drive (on Windows)?

Understanding the Technical Limitation

Alternate Data Streams are a feature of the New Technology File System (NTFS), which is the default file system for Windows operating systems. When you create an ADS, such as file.txt:stream, the data is stored within the Master File Table (MFT) entry of the file on your local disk. This mechanism allows multiple "files" to exist under a single filename, but it is entirely opaque to non-NTFS systems.

Google Drive, regardless of whether you use the desktop sync client or the web interface, treats files as standard byte streams. It does not parse or preserve NTFS-specific metadata attributes. Consequently, when you drag a file containing ADS into your synced Google Drive folder, the sync engine uploads only the primary data stream. The secondary streams are silently discarded because they have no equivalent representation in the cloud storage architecture.

Why Standard Tools Fail

Users often attempt to use PowerShell, Command Prompt, or third-party utilities to verify if their ADS data has been preserved after syncing. These tools operate locally and may show the streams correctly on your C: drive before synchronization. However, once the file is uploaded to Google's servers, the information is gone. If you download that same file again from another machine or after deleting the local version, the downloaded file will lack the original streams.

This behavior is consistent across all Google Drive clients. Whether you are using the "Backup and Sync" legacy tool or the newer "Google Drive for Desktop," the underlying protocol remains the same: it transfers file content and basic properties (like name and modification time), but it ignores extended attributes specific to the host operating system's file system.

Workarounds for Preserving Metadata

If you need to store data associated with a file in the cloud, you must use methods that Google Drive supports natively. Here are two effective strategies to achieve similar results without relying on ADS.

1. Use Sidecar Files

The most robust solution is to create a companion file, often called a sidecar, that holds the additional data. For example, if you have photo.jpg, you can create photo.jpg.meta or photo.json. Store your alternate data in this separate file. Since both files are treated as standard independent entities by Google Drive, both will sync perfectly. You can then write a simple script on your end to associate the two files based on their shared prefix.

2. Embed Data in Filenames or Comments

For small amounts of metadata, consider appending information to the filename itself, though this is less elegant. Alternatively, Google Drive allows you to add comments and descriptions to files via the web interface. While this is manual, it ensures the data is stored in Google's database rather than on the local file system. For programmatic access, the Google Drive API supports custom properties, allowing you to attach key-value pairs to files that persist across platforms.

Local-Only Alternatives

If your workflow strictly requires NTFS Alternate Data Streams, you should avoid syncing those specific files to Google Drive. Instead, keep them in a local folder that is excluded from the sync scope. You can configure the Google Drive for Desktop application to ignore certain directories or file types. This ensures that your critical ADS-containing files remain intact on your local NTFS volume while you sync other necessary documents to the cloud.

Another option is to use a local network share or a self-hosted solution like Nextcloud or OwnCloud, which offer more flexibility regarding extended attributes depending on the backend storage configuration. However, even with these solutions, true NTFS ADS support is rare outside of pure Windows environments.

Risks of Ignoring This Limitation

Assuming that ADS will sync can lead to significant data loss. Scripts that rely on ADS for storing temporary states, hashes, or user preferences may fail silently if the target environment is a cloud-synced directory. Always test your backup and sync procedures rigorously. Verify that every component of your file structure arrives at the destination exactly as intended, including any hidden or auxiliary data.

Frequently Asked Questions

Can I force Google Drive to sync Alternate Data Streams?

No, there is no setting or registry hack that enables this capability. Google Drive's infrastructure is fundamentally incompatible with NTFS extended attributes, and the sync engine will always strip them out during the upload process.

Will downloading a file restore the Alternate Data Streams?

No. Downloading retrieves only the primary data stream that was originally uploaded. Any streams that were present on the source machine but not supported by the cloud service are permanently lost unless you have a local backup that preserves the NTFS structure.

Does Google Drive for Desktop handle ADS differently than the web interface?

No. Both the desktop client and the web interface rely on the same underlying storage protocols. Neither recognizes or preserves NTFS-specific metadata like ADS, permissions, or ownership details.

Are there any cloud services that support NTFS Alternate Data Streams?

Most mainstream consumer cloud services do not support ADS. Self-hosted solutions might allow you to store extended attributes if you configure the backend to support them, but this is complex and not guaranteed. For reliable cross-platform compatibility, stick to standard file attachments or JSON/XML sidecars.

How can I verify if my file still has ADS after syncing?

You can check for ADS on a local NTFS drive using the command dir /r filename in Command Prompt or Get-Item -Path filename -Stream * | Select-Object Stream in PowerShell. If you perform this check on a file synced to Google Drive, you will likely see no additional streams listed, confirming they were not synced.