Introduction

Shrinkr is a macOS CLI tool for batch-compressing images and converting them to modern web formats. It uses a binary search algorithm to hit a target file size while keeping image quality as high as possible — no manual trial-and-error required.

Who it's for

• Developers who need optimized assets before deploying a site
• Photographers cleaning up a shoot before delivery
• Content teams managing image-heavy pages and blogs
• Anyone who wants to shrink a folder of photos without opening Photoshop

What it does

Given a folder of images and a target file size (in KB), Shrinkr:

1. Scans the folder for all supported image files
2. Compresses each image using a binary search to find the optimal quality setting
3. Converts the output to your chosen format (WebP, AVIF, JPEG, or PNG)
4. Saves the results to a separate output folder — originals are never touched
5. Runs all compressions concurrently using a worker pool sized to your CPU core count

Requirements

• macOS (Apple Silicon or Intel via Rosetta 2)
• libvips — installed automatically when using Homebrew