Format

Use the format transformation when a delivered image should use a specific output format, or when Imgwire should choose an appropriate browser-friendly format with auto.

Overview

The format transformation affects the delivered variant, not the original uploaded image. Use it when you want Imgwire to serve a different file format from the same source image.

Common use cases:

• Serve browser-friendly responsive images with format=auto.
• Convert uploads to webp or avif for modern image delivery.
• Force png when the delivered variant needs PNG output.
• Combine format selection with quality=auto for public image delivery.

Syntax

Field	Value
Canonical parameter	format
Aliases	f, ext, extension
Accepted values	auto, jpg, jpeg, png, webp, avif, gif, tiff
Notes	jpg maps to jpeg

Example

https://cdn.imgwire.dev/{organization_id}/{environment_id}/{image_id}?format=auto&quality=auto

image.url({
  format: 'auto',
  quality: 'auto',
});

imgwire images url img_123 --format auto --quality auto

Live examples

The visual content is the same image. The requested output format changes how Imgwire encodes the delivered variant.

Automatic	WebP	JPEG

Best practices

• Use format=auto for most public web image delivery.
• Pair format=auto with Quality set to auto unless the design requires exact quality control.
• Use a specific format when downstream systems require one.
• Keep the original uploaded image unchanged and request different formats as delivery variants.

Common mistakes

• Assuming format=auto changes the uploaded source file. It only changes the delivered variant.
• Forcing one output format everywhere without checking browser and content requirements.
• Hand-building URLs instead of using an SDK helper when format is part of a larger transformation set.

Related pages

• Quality
• Automatic Image Optimization
• Automatic Content Negotiation

Last updated at: May 9, 2026