File Extension Validation Regex (Documents)

Validate document file extensions including pdf, doc, docx, txt, rtf, and odt using regex pattern.

Pattern Breakdown

\.(pdf|doc|docx|txt|rtf|odt)$

Components

Character Classes

• \. - Literal dot (escaped, since . matches any character)
• (pdf|doc|docx|txt|rtf|odt) - Alternation group: matches one of the listed extensions
• $ - End anchor ensures extension is at the end

Examples

Valid:

• document.pdf
• report.doc
• letter.docx
• notes.txt
• document.rtf
• file.odt
• my.document.pdf
• file-name.docx

Invalid:

• document.PDF (uppercase - use case-insensitive flag)
• document.pdf.bak (not at end)
• document (no extension)
• document.jpg (not a document extension)
• .pdf (no filename)
• document.pdf.txt (extension not at end)

Implementation

JavaScript

const docExtRegex = /\.(pdf|doc|docx|txt|rtf|odt)$/i; // 'i' flag for case-insensitive
docExtRegex.test('document.pdf'); // true
docExtRegex.test('report.DOCX'); // true (with 'i' flag)
docExtRegex.test('letter.docx'); // true
docExtRegex.test('image.jpg'); // false (not a document)
docExtRegex.test('document'); // false (no extension)

Python

import re
doc_ext_regex = r'\.(pdf|doc|docx|txt|rtf|odt)$'
bool(re.match(doc_ext_regex, 'document.pdf', re.IGNORECASE))  # True
bool(re.match(doc_ext_regex, 'report.DOCX', re.IGNORECASE))  # True
bool(re.match(doc_ext_regex, 'image.jpg', re.IGNORECASE))  # False

Go

docExtRegex := regexp.MustCompile(`(?i)\.(pdf|doc|docx|txt|rtf|odt)$`) // (?i) for case-insensitive
docExtRegex.MatchString("document.pdf") // true
docExtRegex.MatchString("report.DOCX") // true
docExtRegex.MatchString("image.jpg") // false

Limitations

1. Case-sensitive by default: Requires case-insensitive flag for uppercase extensions
2. No MIME type validation: Only checks extension, not actual file content
3. Limited extensions: Only covers common document formats
4. No filename validation: Doesn't validate the filename part
5. Extension spoofing: Can be bypassed by renaming files
6. Missing formats: Doesn't include xls, xlsx, ppt, pptx, etc.

When to Use

• Document file upload validation
• File type filtering
• Quick extension checking
• Client-side validation
• When you need to filter document files

For production, consider:

• Using case-insensitive matching
• Validating actual file content (MIME type)
• Checking file signatures/magic numbers
• Supporting additional document formats (xls, xlsx, ppt, pptx, etc.)
• Server-side validation (never trust client-side only)