File Extension Validation Regex (Images)

Validate image file extensions including jpg, jpeg, png, gif, bmp, and svg using regex pattern.

Pattern Breakdown

\.(jpg|jpeg|png|gif|bmp|svg)$

Components

Character Classes

• \. - Literal dot (escaped, since . matches any character)
• (jpg|jpeg|png|gif|bmp|svg) - Alternation group: matches one of the listed extensions
• $ - End anchor ensures extension is at the end

Examples

Valid:

• image.jpg
• photo.jpeg
• picture.png
• animation.gif
• bitmap.bmp
• vector.svg
• my.image.png
• file-name.jpeg

Invalid:

• image.JPG (uppercase - use case-insensitive flag)
• image.jpg.txt (not at end)
• image (no extension)
• image.pdf (not an image extension)
• .jpg (no filename)
• image.jpg.backup (extension not at end)

Implementation

JavaScript

const imageExtRegex = /\.(jpg|jpeg|png|gif|bmp|svg)$/i; // 'i' flag for case-insensitive
imageExtRegex.test('image.jpg'); // true
imageExtRegex.test('photo.PNG'); // true (with 'i' flag)
imageExtRegex.test('picture.png'); // true
imageExtRegex.test('document.pdf'); // false (not an image)
imageExtRegex.test('image'); // false (no extension)

Python

import re
image_ext_regex = r'\.(jpg|jpeg|png|gif|bmp|svg)$'
bool(re.match(image_ext_regex, 'image.jpg', re.IGNORECASE))  # True
bool(re.match(image_ext_regex, 'photo.PNG', re.IGNORECASE))  # True
bool(re.match(image_ext_regex, 'document.pdf', re.IGNORECASE))  # False

Go

imageExtRegex := regexp.MustCompile(`(?i)\.(jpg|jpeg|png|gif|bmp|svg)$`) // (?i) for case-insensitive
imageExtRegex.MatchString("image.jpg") // true
imageExtRegex.MatchString("photo.PNG") // true
imageExtRegex.MatchString("document.pdf") // 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 image formats
4. No filename validation: Doesn't validate the filename part
5. Extension spoofing: Can be bypassed by renaming files

When to Use

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

For production, consider:

• Using case-insensitive matching
• Validating actual file content (MIME type)
• Checking file signatures/magic numbers
• Supporting additional image formats if needed
• Server-side validation (never trust client-side only)