When comparing Harp vs Gatsby JS, the Slant community recommends Gatsby JS for most people. In the question“What are the best static site generators?” Gatsby JS is ranked 12th while Harp is ranked 30th.
Ranked in these QuestionsQuestion Ranking
Pro Compiles assets on request
Rather than regenerate the whole site when a file changes, Harp only reloads what is necessary, keeping the compile time fast.
Pro Supports popular languages
Harp supports a large variety of languages, including Jade, CoffeeScript, Stylus and Sass. See the full list here.
Pro No page reload when navigating
Pro Live reload
Every change you make can be almost immediately seen in a browser.
Pro Based on React.js
Editing markup is phenomenally easy when you have components.
Pro Beautiful out-of-the-box blog starters
Con Limited extensibility
There are no plugins available to extend the functionality or language support of Harp.
Con A bit raw
You'll maybe have to tweak some JSX if you want something that's not covered by available themes.