Tools for Optimizing SVG

Command Line Tools
SVGO (Seems like the biggest player)Scoursvgcleaner
Unfortunately, none¹ of them are maintained anymore. You also don’t need to use just one².
SVGO with a Task Runner
grunt-svgmingulp-svgmingulp-svgosvgo-loader (webpack)
Desktop Apps
ImageOptim (macOS)macOS “folder action” Before macOS 10.15 Catalina, you could use SVGO GUI, but it’s 32-bit which makes it obsolete.
There are generic app for optimizing images on Windows and Linux, but I haven’t yet confirmed any of them do SVG.
Web Apps
The idea with these tools is that you have an SVG on your machine and you upload it to this web app to optimize this one SVG.
SVGOMGNanoKrakenSVG MinifierSVG optimisersvg-editor
APIs
ImageOptim Web Service APIKrakenImgix supports SVG if you opt-in. It’s not entirely clear if Cloudinary actually optimizes SVG, and their API is uploading-focused, but they do support “transformations” on SVG, and their fetch URL format is API-like.
Optimizing Directly Out of Design Tools
Typically, when you export SVG out of a design tool it is in dire need of optimization. Hence, all the tools in this article. The design tool itself can help though, at least somewhat.
Sketch’s svgo-compressor (there is also a Sketch-specific web app for this called SVGito)Figma does its best by defaultIllustrator has SVG NOWInkscape can export as “Optimized SVG” (uses Scour internally) or use SVGO-Inkscape
Deep Dive Articles
Michelle Barker: Optimising SVGs for the WebJayden Seric: How to optimize SVGSara Soueidan: Tips for Creating and Exporting Better SVGs for the Web & Useful SVGO[ptimization] ToolsCosima Mielke: Tools And Resources For Editing, Converting And Optimizing SVG Jake Giltsoff: SVG on the Web, Preparing & OptimisingAndreas Larsen: Optimising SVGs for Web UseJosh Stoik: Optimizing SVGs For Web Use
Manual/Hand SVG Optimization Work
Raymond Schwartz: Understanding and Manually Improving SVG OptimizationAmberd Design Studio: How to Optimize an SVG File Step-by-StepVideo from us: Reducing vector points in IllustratorVideo from Kevin Powell: How to create, clean up, and optimize an SVGPresentation by Brenda Storer: Cracking the SVG Code Dudley Storey: SVG Optimisation: The Basics
No longer maintained references: SVGO, Scour, svgcleanerJohannes Kalliauer at Wikipedia (who informed me of the broader landscape of command-line tools) tells me that each of the tools have their advantages. While SVGO is popular, it is also the buggiest. svgcleaner is the fastest. Scour and svgcleaner can also repair damaged SVG while SVGO cannot.