lightweight SVG viewer

You have quite the diverse range of options:

Free:

Gapplin (AppStore) 14MB

macSVG 9MB

macSVG is a MIT-licensed open-source macOS application for designing and editing Scalable Vector Graphics (SVG) content for HTML5 web pages, mobile apps, animation design, and general graphics usage.

SVGViewer

Fast, Free and Simple SVGViewer file Viewer Open and export SVG files on Mac, send to friends. Download SVGViewer for Mac. It’s free!

And with an additional footprint of 0 bytes:

• your favourite browser!

I saw this question pretty late. Another option is to use svg-edit It is browser based, and you can download the entire application and runs in your web browser.

They also have an online version. see SVG editor