Restrictions

Filename, length, and file extension rules help ensure compatibility with external systems, reduce failed transfers, and support compliance requirements. Enforcing these rules at upload time prevents disruptions before files enter automated workflows or downstream systems.

Many external systems and remote servers impose strict filename and file type limits. Applying these rules at the folder level improves automation reliability, supports consistent processing, and keeps files organized as file volumes grow.

These restrictions apply when files or folders are placed directly into a folder. Move and copy operations succeed only when the destination path is no more restrictive than the source path.

How Restrictions Are Enforced

Files.com provides built in controls to enforce these requirements on uploads. You can limit uploaded files by filename length, restrict filenames using regular expressions, and allow or block specific file extensions. These settings apply at the folder level and can be inherited by subfolders, giving you precise control over how files enter your environment while supporting compliance, reliable automation, and downstream compatibility.

Moving or Copying Files into Restricted Folders

Move and copy operations fail when the destination path has filename related restrictions that are stricter than the source path. This includes filename length limits, file extension rules, and regular expression based filename rules.

If any folder in the destination path enforces stricter rules, the system blocks the entire move or copy operation rather than attempting to validate each file.

This behavior is intentional. For protocols including SFTP, checking filename restrictions during move or copy operations would require inspecting every file in the operation, which would significantly slow transfers and reduce reliability. To maintain predictable behavior and system reliability, the system uses a fast fail approach instead of per file validation. For example, if a destination folder enforces a stricter filename length or extension rule than the source, the move or copy operation fails immediately rather than checking each file.

To prevent move or copy failures, do not configure stricter filename length, file extension, or regular expression based rules on folders when files need to be moved or copied into those locations.

Automations and Renaming Considerations

If you use a Files.com automation that requires special handling on the source file names, refer to File Name Pattern Matching. For renaming destination files, see the guidelines on customizing destination filenames.

Use Cases

Here are some common scenarios where applying filename, file type, or folder structure restrictions can help prevent errors, maintain compatibility, and protect your workflow.

Operating System & Cross-Platform Compatibility

Different operating systems have filename restrictions. For example, Windows does not allow characters like \ / : * ? " < > |, while UNIX-based systems may enforce limitations on special characters or case sensitivity. A filename that works in one system may cause errors or be inaccessible in another (e.g., Linux vs. Windows). Enforcing filename rules using Limit Uploaded Files to Regular Expression helps ensure seamless file transfers across platforms.

Counterparty & Workflow Compatibility

Some external systems and workflows only accept specific file extensions. If an unsupported file type is uploaded, these systems may fail, crash, or behave unpredictably. Enforcing restrictions using Limit Uploaded Files to Certain File Extensions ensures files remain compliant with expected formats.

Remote Server Limitations

Certain remote servers do not support specific file types, symbolic variables, or filenames exceeding a defined length. Using Limit Uploaded Files to Certain File Extensions or Limit Uploaded Files to Regular Expression prevents upload failures and unexpected behavior when interacting with these servers.

File Name Length Restrictions

Many systems impose filename or path length limits, and exceeding these can cause transfer or processing errors. Enforcing restrictions using Limit Uploaded Files by File Name Length helps prevent issues caused by excessively long filenames.

Preventing Disruptions in Automated Workflows

If your team relies on automation, such as scheduled syncs, file transfers, or integrations with external systems, an accidental folder move can cause failures or misrouted data. Locking subfolders ensures that workflows function without unexpected interruptions.

Protecting Shared Project Directories

In collaborative environments, project files may be stored in a structured hierarchy. If a user unintentionally moves or renames a folder, team members may lose access to essential files or disrupt version control. Locking the folder structure ensures everyone can access files as expected without modifying the organization.

Security & Hidden File Considerations

Restricting certain file types helps prevent the accidental or malicious upload of executable files (.exe, .sh, .bat), scripts, or hidden files (e.g., .filename) that external systems may ignore or block. Using Limit Uploaded Files to Certain File Extensions or Limit Uploaded Files to Regular Expression ensures only safe and intended files are uploaded.

Compliance & Regulatory Requirements

Certain industries require strict file controls to comply with HIPAA, GDPR, or SOX. Using Limit Uploaded Files to Certain File Extensions ensures that only permitted file types are stored or transferred, minimizing regulatory risks.

Symbolic Variables & Naming Conflicts

Some counterparty systems use symbolic variables (e.g., $, %, {}) in filenames for automation or templating. Allowing unrestricted filenames may cause misinterpretation, conflicts, or unintended execution of system commands. Using Limit Uploaded Files to Regular Expression prevents filenames containing these characters.