Image MIME Reference
PJPEG
Progressive JPEG (Legacy IE Alias)
image/pjpeg
VS
QuickTime Image Format
image/x-quicktime
QTIF
A complete technical comparison of Progressive JPEG (Legacy IE Alias) and QuickTime Image Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
PJPEG wins on browser support
Feature Support
| Feature | PJPEG | QTIF |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
Progressive JPEG (Legacy IE Alias)
image/pjpeg
Extension
.jpeg.jpg.pjpeg.pjp.jfif
Container
JPEG (ISO/IEC 10918-1)
Compression
Lossy (DCT)
Algorithm
Discrete Cosine Transform (DCT)
Color Depth
8-bit, 12-bit
Developed by
Joint Photographic Experts Group / Microsoft (Alias)
Released
1992
Magic Bytes
FF D8 FF E0 (JFIF) / FF D8 FF E1 (Exif)
QuickTime Image Format
image/x-quicktime
Extension
.qtif.qti.qif
Container
QuickTime Atom Container
Compression
Varies (JPEG, SMC, Apple Video, Cinepak, Uncompressed)
Algorithm
QuickTime Image Compression Manager (ICM) Codecs
Color Depth
1-bit to 32-bit (Varies depending on the enclosed codec)
Developed by
Apple Computer, Inc.
Released
1991
Magic Bytes
Varies (Typically begins with a 32-bit size integer followed by 69 64 73 63 ('idsc'))
Browser Support Comparison
| Browser | PJPEG | QTIF |
|---|---|---|
Chrome
|
✓ All
|
✕ |
Firefox
|
✓ All
|
✕ |
Safari
|
✓ All
|
✕ |
Edge
|
✓ All
|
✕ |
IE (Legacy)
|
✓
|
✕ |
PJPEG
PJPEG Strengths
- Progressive JPEGs (which this MIME type attempted to describe) provide excellent perceived loading speeds on slow connections by rendering a low-resolution preview first
- Files sent with this MIME type are fully backwards compatible with any standard JPEG decoder
Limitations
- It is a non-standard MIME type that violates IANA specifications
- Causes strict file upload validation scripts to fail if not explicitly whitelisted or mapped
- Creates unnecessary confusion, as the official image/jpeg MIME type already fully encompasses progressive encoding
QTIF
QTIF Strengths
- Extremely flexible architecture allowing it to encapsulate virtually any image compression algorithm available on the host machine
- Supported 32-bit images with alpha channels (transparency) long before PNG became an established standard
Limitations
- Fundamentally tied to Apple's deprecated QuickTime architecture, rendering the files almost entirely unreadable on modern systems without specialized legacy software or FFmpeg
- The 'wrapper' nature of the format means that even if a parser can read the QTIF container, it may fail to render the image if it lacks the specific proprietary codec (like Apple SMC) used to compress the pixel data
- Zero native support in modern web browsers
When to choose which format
PJPEG
Use PJPEG when…
- Legacy Internet Explorer File Uploads
- Progressive Image Rendering (Historical context)
QTIF
Use QTIF when…
- Classic Mac OS Applications and Backgrounds
- QuickTime VR Panorama Textures
- 1990s CD-ROM Multimedia Assets