Free webp to jpg
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Image MIME Reference
JXL

JPEG XL

image/jxl
VS

Portable Network Graphics (Legacy MIME)

image/x-png
PNG

A complete technical comparison of JPEG XL and Portable Network Graphics (Legacy MIME) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

PNG wins on browser support

Feature Support

Feature JXL PNG
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading Yes Yes
HDR Support Yes Yes
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
JPEG XL
image/jxl
Extension
.jxl
Container ISOBMFF / JPEG XL Codestream
Compression Lossy (VarDCT) / Lossless (Modular)
Algorithm
VarDCT (Variable block-size DCT)Modular (Predictive coding for lossless)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit, 32-bit (Float)
Developed by Joint Photographic Experts Group (JPEG)
Released 2021
Magic Bytes
FF 0A (Codestream) / 00 00 00 0C 4A 58 4C 20 0D 0A 87 0A (Container)
Full JXL reference →
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
Full PNG reference →

Browser Support Comparison

Browser JXL PNG
Chrome Chrome
✕
✓ 1
Firefox Firefox
✕
✓ 1
Safari Safari
✓ 17+
✓ 1
Edge Edge
✕
✓ 12
IE IE (Legacy)
✕
✓
JXL

JXL Strengths

  • Capable of losslessly recompressing legacy JPEG files, saving ~20% space while retaining perfect byte-for-byte restorability
  • Highly superior progressive decoding (Saliency-driven), allowing recognizable images to load extremely fast on slow connections
  • Outperforms WebP and competes favorably with AVIF, especially at high-fidelity settings and for complex textures/photography
  • Royalty-free with an open-source reference implementation (libjxl)
Limitations
  • Google's removal of JXL support from Chrome severely hindered its adoption as a universal web standard
  • Lack of hardware decoding chips compared to video-derived codecs like AVIF (AV1)
  • File parsing logic is complex due to the split between raw codestreams and ISOBMFF containers
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

JXL
Use JXL when…
  • High-End Web Delivery (via Safari/Polyfills)
  • HDR Photography
  • Legacy JPEG Archiving
  • Digital Art & Image Storage
PNG
Use PNG when…
  • Legacy Internet Explorer File Uploads
  • Older ASP/PHP Web Applications
  • Lossless Web Graphics

More comparisons

JXL vs ACES → PNG vs ACES → JXL vs APNG → PNG vs APNG → JXL vs AVCI → PNG vs AVCI → JXL vs AVCS → PNG vs AVCS → JXL vs AVIF → PNG vs AVIF → All comparisons →
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