eCTD File Naming Conventions: The Complete Guide to Compliant Document Names

eCTD file naming conventions are the standardized rules defined by ICH M8 that govern how documents, folders, and paths must be named within Electronic Common Technical Document (eCTD) submissions. These naming conventions specify character limits, allowed characters, case requirements, and structural rules that regulatory gateways enforce during validation.

Getting file names wrong is one of the fastest ways to trigger a gateway rejection.

The frustrating reality is that most file naming errors are entirely preventable. A document named Clinical Study Report (Final).PDF contains four separate naming violations that will fail validation, yet these errors often go unnoticed until the critical moment of submission.

In this guide, you'll learn:

• Complete eCTD file naming rules with character limits and allowed characters
• Folder naming conventions and path length requirements
• Regional differences between FDA, EMA, and Health Canada naming requirements
• The 12 most common file naming errors and how to prevent them
• Step-by-step process for fixing non-compliant file names

What Are eCTD File Naming Conventions?

eCTD file naming conventions are the technical specifications that define how every document and folder in an eCTD submission must be named. These conventions are part of the ICH M8 specification and are enforced by all regulatory agency gateways including FDA ESG, EMA CESP, and Health Canada CESR.

Key characteristics of eCTD file naming conventions:

• Maximum file name length of 64 characters including extension
• Only lowercase letters (a-z), numbers (0-9), and hyphens (-) are allowed
• Spaces, uppercase letters, and special characters are prohibited
• File extensions must be lowercase (.pdf not .PDF)
• Total path length has recommended limits varying by region
• Folder names follow the same character rules with specific structural requirements

Understanding eCTD file naming conventions is essential because these rules are enforced automatically at the gateway level. Unlike content issues that reviewers identify during assessment, file naming violations trigger immediate rejection before your submission even reaches a human reviewer.

eCTD Naming Rules: Character Requirements

The eCTD naming rules specify exactly which characters are permitted in file names and folder names. Violations of these character requirements are the primary cause of file naming validation errors.

Allowed Characters in eCTD File Names

Character Rules by File Name Component

File Name Length Limits

The eCTD naming requirements specify strict length limits:

File Name Length Calculation:

eCTD File Names: Folder Naming Conventions

eCTD file names and folder names follow similar rules, but folders have additional structural requirements based on their position in the eCTD module hierarchy.

ICH M8 Folder Naming Structure

The eCTD specification defines standard folder names for each module section:

Module-Specific Folder Naming

Module 1 Folder Naming (FDA Example):

Module 3 Folder Naming:

Folder Naming Rules Summary

Complete Path Examples

Valid eCTD Paths:

Invalid eCTD Paths:

eCTD Naming Requirements: Path Length Specifications

The eCTD naming requirements include specifications for total path length that vary by region and technical environment. Understanding path length limits prevents truncation errors and system compatibility issues.

Regional Path Length Requirements

Path Length Calculation

Total path length includes:

• Sequence folder (e.g., 0000/)
• Module folder (e.g., m3/)
• All subfolders (e.g., 32-body-data/32s-drug-sub/)
• File name with extension (e.g., drug-substance-specification.pdf)

Example Path Length Calculation:

Path Length Best Practices

CTD File Naming: Regional Differences

CTD file naming requirements are largely harmonized across regions, but subtle differences exist that can cause validation failures when preparing multi-regional submissions.

FDA vs EMA vs Health Canada File Naming Comparison

Regional Folder Name Differences

Module 1 Regional Variations:

Multi-Regional Submission Considerations

When preparing eCTD submissions for multiple regions, follow the most restrictive naming rules:

Common eCTD File Naming Errors

Understanding the most frequent eCTD file naming errors helps you prevent validation failures and gateway rejections. These 12 errors account for the majority of naming-related submission problems.

The 12 Most Common File Naming Errors

Error Category Analysis

Common Error Patterns by Source System

How to Fix eCTD File Naming Errors

When you discover file naming errors in your eCTD submission, systematic correction prevents missing violations and ensures all documents pass validation.

Step-by-Step File Name Correction Process

Step 1: Identify All Non-Compliant Files

Run validation to generate a complete list of naming errors:

• Use eCTD publishing tool validation
• Run dedicated file naming check
• Review validation report for all naming violations

Step 2: Categorize Errors

Step 3: Apply Naming Corrections

For individual files:

1. Identify the non-compliant element
2. Rename following the conventions
3. Update all references to the file
4. Regenerate XML backbone
5. Recalculate MD5 checksum

For bulk corrections:

1. Export list of non-compliant files
2. Create mapping of old names to new names
3. Execute batch rename operation
4. Update backbone.xml references
5. Regenerate all checksums
6. Re-validate entire submission

File Name Transformation Examples

Checksum Regeneration After Renaming

Checksum update process:

1. Rename the file
2. Calculate new MD5 checksum
3. Update the checksum attribute in backbone.xml
4. Update the xlink:href path if location changed
5. Validate the submission again

eCTD File Naming Best Practices

Following eCTD file naming best practices from the start of document creation prevents costly corrections and submission delays.

Document Creation Best Practices

Naming Convention Framework

Recommended naming pattern:

Examples using this pattern:

Pre-Publishing Checklist

Before final eCTD assembly, verify all file names against this checklist:

Automated Validation Tools

eCTD File Naming Validation Error Messages

Understanding validation error messages helps you quickly identify and correct file naming issues during eCTD preparation.

Common Validation Error Messages

Validation Error Message Reference Table

Gateway-Specific Error Messages

FDA ESG Error Messages:

EMA CESP Error Messages:

Key Takeaways

Next Steps

Implementing correct eCTD file naming conventions prevents validation failures and gateway rejections, but manually checking thousands of files across a submission is error-prone and time-consuming. Automated validation catches naming errors before they delay your submission.

Need help validating eCTD file names? Assyro's AI-powered platform validates all file naming conventions automatically, checking character compliance, length limits, path lengths, and regional requirements across your entire submission. Catch naming errors before they become gateway rejections.

Organizations managing regulatory submissions benefit from automated validation tools that catch errors before gateway rejection. Assyro's AI-powered platform validates eCTD submissions against FDA, EMA, and Health Canada requirements, providing detailed error reports and remediation guidance before submission.

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