Image MIME Reference
JPEG
JPEG Image
image/jpeg
VS
Portable Network Graphics (Legacy MIME)
image/x-png
PNG
A complete technical comparison of JPEG Image and Portable Network Graphics (Legacy MIME) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JPEG | PNG |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | Yes |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | Yes | Yes |
| ICC Color Profile | Yes | Yes |
JPEG Image
image/jpeg
Extension
.jpg.jpeg.jpe.jfif
Container
JFIF / Exif
Compression
Lossy
Algorithm
DCT (Discrete Cosine Transform)
Color Depth
8-bit
Developed by
Joint Photographic Experts Group
Released
1992
Magic Bytes
FF D8 FF
Portable Network Graphics (Legacy MIME)
image/x-png
Extension
.png
Container
PNG Chunk Structure (IHDR, IDAT, IEND)
Compression
Deflate (Lossless)
Algorithm
Deflate (LZ77)
Color Depth
1-bit to 16-bit (Grayscale), 8-bit (Indexed Palette), 24-bit (True Color), 32-bit (True Color with Alpha), 48-bit (High Color), 64-bit (High Color with Alpha)
Developed by
PNG Development Group
Released
1996
Magic Bytes
89 50 4E 47 0D 0A 1A 0A
Browser Support Comparison
| Browser | JPEG | PNG |
|---|---|---|
Chrome
|
✓ All
|
✓ 1
|
Firefox
|
✓ All
|
✓ 1
|
Safari
|
✓ All
|
✓ 1
|
Edge
|
✓ All
|
✓ 12
|
IE (Legacy)
|
✓
|
✓
|
JPEG
JPEG Strengths
- Universal support — every browser, OS, and application handles JPEG
- Excellent compression for complex photographs with natural color gradients
- Rich metadata support: EXIF (GPS, camera settings), ICC color profiles
Limitations
- No transparency — cannot have a transparent background
- Lossy compression introduces visible artifacts on sharp edges and text
- No animation support
PNG
PNG Strengths
- The underlying format provides flawless, lossless compression and perfect 8-bit alpha channel transparency
- Universally supported by every modern operating system, image editor, and web browser
Limitations
- The 'image/x-png' string is an obsolete vendor quirk that forces backend developers to write redundant normalization logic in file upload scripts
- If left unnormalized, strict MIME validators or content security policies on modern systems may incorrectly reject valid PNG files
When to choose which format
JPEG
Use JPEG when…
- Photography
- Websites
- Social Media
PNG
Use PNG when…
- Legacy Internet Explorer File Uploads
- Older ASP/PHP Web Applications
- Lossless Web Graphics