Automatic Format Selection

When no output format is specified, Openinary automatically selects the smallest format the requesting browser supports.

How it works

Detect browser support

Reads the Accept header and User-Agent to determine which modern formats are supported.

Analyze content

Evaluates whether the image is a photo, graphic, or contains transparency to pick the best codec.

Pick the smallest result

Encodes in candidate formats, compares sizes, and serves the winner.Priority: AVIF → WebP → JPEG / PNG

Original format	→ AVIF	→ WebP
JPEG	40–50% smaller	25–35% smaller
PNG	50–70% smaller	25–40% smaller

Actual savings depend on image content and original compression level.

Use the f parameter to force a specific format regardless of browser support.

GET /t/f_avif,q_80/image.jpg
GET /t/f_webp,q_85/image.jpg
GET /t/f_jpeg,q_90/image.jpg

Full reference for resize, crop, rotate, and format parameters.

Pre-generate optimized variants at upload time.