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Format Parameters

fm - Format Conversion

The fm parameter is used to convert the image to a specified format. The following image formats are supported:

  • JPEG - Universal compatibility, excellent for photographs
  • PNG - Transparency support, ideal for graphics with alpha channel
  • GIF - Animation support, legacy format
  • WebP - Modern format with superior compression
  • AVIF - Next-generation format with excellent compression
  • JXL - JPEG XL format for advanced compression

q - Output Quality

The q parameter controls the output quality of the image for lossy formats, including JPEG, WebP, AVIF, and JXL.

Type: integer or string
Range: 0 - 100 or quality strings
Default: 75 (or 45 with Save-Data client hint)

Quality Values

  • 0-30: Low quality, smallest file size
  • 30-60: Medium quality, balanced size/quality
  • 60-85: High quality, larger file size
  • 85-100: Maximum quality, largest file size

Quality Strings

The following quality strings are supported for automatic quality optimization:

  • auto - Automatic quality selection
  • auto:high - High quality automatic selection
  • auto:med - Medium quality automatic selection
  • auto:low - Low quality automatic selection

Usage

Format Conversion

image.jpg?fm=webp
Convert JPEG to WebP format.

Quality Control

image.jpg?fm=jpeg&q=85
High quality JPEG output.

Automatic Quality

image.jpg?fm=webp&q=auto
Automatic quality optimization.

Next-Generation Formats

image.jpg?fm=avif&q=75
Convert to AVIF with 75% quality.

Format Guide

JPEG

  • Best for: Photographs, complex images
  • Compression: Lossy
  • Transparency: No
  • Browser support: Universal

PNG

  • Best for: Graphics, logos, transparency needed
  • Compression: Lossless
  • Transparency: Yes
  • Browser support: Universal

WebP

  • Best for: Web optimization, modern browsers
  • Compression: Lossy/Lossless
  • Transparency: Yes
  • Browser support: Modern browsers (95%+)

AVIF

  • Best for: Maximum compression efficiency
  • Compression: Lossy/Lossless
  • Transparency: Yes
  • Browser support: Growing (80%+)

JXL (JPEG XL)

  • Best for: Future-proof high efficiency
  • Compression: Superior lossy/lossless
  • Transparency: Yes
  • Browser support: Limited (experimental)

Examples

Web Optimization

image.jpg?fm=webp&q=auto

E-commerce Products

product.jpg?fm=webp&q=85&w=800&h=800

Logo/Graphics

logo.png?fm=webp&q=100

Mobile Optimization

hero.jpg?fm=avif&q=auto:med&w=800