Open source · Since May 2014

Slimsy

Responsive images for Umbraco, first released in May 2014 and introduced by Umbraco founder Niels Hartvig in the Codegarden 2014 keynote. Twelve years on, Slimsy is still maintained, and it is one of the oldest open-source Umbraco packages still supported.

Slimsy icon
May 2014
First released
12 years
In use and still supported
Around 300,000
NuGet downloads
MIT
Open-source licence

A pioneer of responsive images in Umbraco

Slimsy dates from the early days of responsive web design, when browsers had no built-in way to serve each screen the right image. In May 2014 Jeavon Leopold set out the approach in a guest post on umbraco.com: adaptive images built on Umbraco's Image Cropper, written while the picture element was still being specified. Slimsy packaged that work, so any Umbraco 7 site could use it. Umbraco's founder, Niels Hartvig, also introduced Slimsy in the Codegarden 2014 keynote (Vimeo, 32:05).

It has been kept up to date as Umbraco has changed, and Slimsy 7 now supports Umbraco 17 and 18. It is built on the work of the LazySizes and ImageSharp projects. It has been built with contributions from William Phillips and Marc Stöcker, among others, and its name was suggested by community member Douglas Robar.

How Slimsy has grown

  1. May 2014: first release

    Responsive, retina-ready images for Umbraco 7, using the Image Cropper and the Slimmage adaptive-imaging library, before the picture element was settled.

  2. Codegarden 2014: on the keynote stage

    Umbraco founder Niels Hartvig introduced Slimsy in the Codegarden 2014 keynote.

  3. Slimsy 3 for Umbraco 8

    A complete rebuild of version 2 for Umbraco 8. It could turn an image inside a rich text editor or grid into a multi-source picture element, served through a CDN such as Azure CDN.

  4. September 2022: Slimsy 4 for Umbraco 10

    Rebuilt on ImageSharp.Web with the slimsy-picture tag helper, after hundreds of hours of work and a beta period.

  5. June 2023: AVIF

    Slimsy 4.1 added AVIF through Cloudflare Image Resizing. In tests on the Crumpled Dog website, AVIF was mostly 10% to 22% smaller than WebP at 70% quality. Slimsy also supports WebP and low-quality image placeholders.

  6. Today

    Slimsy 6 arrived on its tenth anniversary in May 2024, for Umbraco 14. Slimsy 7 supports Umbraco 17 and 18, and is still maintained.

Recommended in Umbraco's own documentation

Slimsy is named in the image optimisation guide in Umbraco's sustainability best practices, as the package that makes it easier to set up picture elements with fallback image formats and screen-size-based image selection. The guide also says it can be combined with CloudflareImageUrlGenerator for image delivery through Cloudflare.

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License
MIT