Regex Pattern Library

File Extension

Extract file extensions from filenames and paths.

What Is This?

This regex pattern extracts the file extension from a filename or path. It matches a dot followed by one or more word characters at the end of a string. The extension is captured in group 1 for easy extraction. For example, from 'document.pdf' it captures 'pdf'.

How to Use This Pattern

1

Pattern

\.(\w+)$

\.(\w+)$
2

Usage

Use this pattern to extract file extensions for file type checking, routing, or content-type detection. The captured group 1 contains the extension without the dot. Be aware that some files have multiple extensions (.tar.gz) or no extension at all.

Examples

Common extensions

Matches: document.pdf, image.jpg, script.js, styles.css, archive.tar.gz. Non-matches: README, Makefile, .gitignore, file

Path handling

Matches: /path/to/file.html, C:\Users\file.docx, ~/config.json. Non-matches: file., noextension, file.

Related Entries

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Match URL-friendly slugs with lowercase letters, digits, and hyphens.

HTML Tag

Match HTML tags including opening, closing, and self-closing tags with attributes.

Whitespace Normalization

Match leading, trailing, and consecutive internal whitespace for normalization.

Frequently Asked Questions

Does this work for files with multiple extensions?

This pattern captures only the last extension (e.g., 'gz' from 'archive.tar.gz'). To capture all extensions, use \.([\w.]+)$ or a different approach. For most use cases, the last extension is sufficient.

How do I handle hidden files (like .gitignore)?

Hidden files without a base name (starting with a dot) are edge cases. The pattern would match 'gitignore' as the extension of '.gitignore'. For these cases, check if the filename itself is just an extension.

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