Restrictions

Filename, length, and file extension rules keep files compatible with external systems, reduce failed transfers, and support compliance requirements. Applying them at upload time prevents disruptions before files enter automated workflows or downstream systems.

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.

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 validating 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. The system uses a fast-fail approach instead of per-file validation. 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

Filename, file type, and folder structure restrictions cover several common scenarios.

Operating System and Cross-Platform Compatibility

Different operating systems have different filename restrictions. Windows does not allow the characters \ / : * ? " < > |, 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. Use Limit Uploaded Files to Regular Expression to enforce filename rules that work across platforms.

Counterparty and 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. Use Limit Uploaded Files to Certain File Extensions to keep files within the expected formats.

Remote Server Limitations

Certain remote servers do not support specific file types, symbolic variables, or filenames exceeding a defined length. Use Limit Uploaded Files to Certain File Extensions or Limit Uploaded Files to Regular Expression to prevent 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. Use Limit Uploaded Files by File Name Length to prevent issues caused by excessively long filenames.

Preventing Disruptions in Automated Workflows

When 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 keeps workflows running 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 preserves access to files without modifying the organization.

Security and Hidden File Considerations

Restricting certain file types helps prevent the accidental or malicious upload of executable files (.exe, .sh, .bat), scripts, or hidden files (such as .filename) that external systems may ignore or block. Use Limit Uploaded Files to Certain File Extensions or Limit Uploaded Files to Regular Expression to restrict uploads to safe and intended files.

Compliance and Regulatory Requirements

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

Symbolic Variables and Naming Conflicts

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