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 8th while Harp is ranked 29th.
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 Based on React.js
Editing markup is phenomenally easy when you have components.
Pro Live reload
Every change you make can be almost immediately seen in a browser.
Pro Open Source
Pro A static site and a React app in one
The static pages are generated by Server Site Rendering of the React app. So you have all benefits of a static site, and all benefits of a React app, which is very powerful.
Pro Take content from any source
Gatsby can generate the pages with content from any sources like Drupal, Wordpress, Contentful, etc. If the source plugin is not coded for your solution, you can create it.
Pro A lot of plugins
Gatsby offers a lot of plugins to integrate tools like SASS, typescript, styled components, etc.
Pro Very active development
Gatsby is very actively developed and the maintainers are very helpful.
Pro A lot of examples
Gatsby have a lot of examples sites in his github repository.
Pro GraphQL Data Layer
Pro Beautiful out-of-the-box blog starters
Pro Built-in code and data splitting
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.