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Software tooling & tips

How to find and remove dead CSS

People hate maintaining CSS for lots of reasons, but figuring out if it's safe to delete old styles is a vexing problem without any great solutions. Here's one way to do it by using, of all things, code coverage!
Justin Searls
|
June 3, 2021
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Do you have a pile of old CSS styles that you’re pretty sure are no longer referenced anywhere, but that you’re nevertheless afraid to delete because you have no way to be sure that no musty corners of your site somehow depend on them to render correctly?

I’ve been saying for years that the most valuable uses for code coverage have nothing to do with testing, and today I was happy to add another great use case: gaining confidence over which styles are actually safe to delete. The approach in this screencast shows a way to record and combine the code coverage results for our site’s CSS across each web page.

Other automated approaches for identifying dead styles exist, but modern CSS has introduced so many context-dependent selectors (e.g. media queries and pseudo-elements) that nothing can beat recording coverage while manually resizing and clicking around your custom components like only you know how.

Stuff covered in this video:

  • How we use our static-rails gem to host our static blog & website inside a Rails API monorepo
  • CSS Tricks' overview on this topic
  • A tutorial on Chrome’s DevTools Coverage drawer
  • The DisCoverage Chrome extension for munging multiple coverage exports

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Understanding legacy application rewrite vs. refactor tradeoffs

Understanding legacy application rewrite vs. refactor pros and cons can be difficult, especially if you’ve never experienced the possibility of changing it for the better. Let's look at a few examples to learn more and outline a small decision making framework to help you evaluate your path forward.

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Pydantically perfect: seamlessly handle non-Pythonic naming conventions

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Field Report: Rails World 2025

Double Agent Mike Bowman shares a field report on the Rails World 2025 experience, including highlights from favorite talks, the venue, and the Ruby Embassy.

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