Slim review
A focused Ruby templating engine for teams that prefer concise, indentation-based markup.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Slim is a Ruby template language and engine for generating markup in web views. Its indentation-based syntax avoids required closing tags, making it a fit for Ruby teams that want concise templates and are comfortable with a distinct markup style. Templates can use Ruby expressions and control flow, and HTML output is escaped by default. Slim is distributed as a Ruby gem under the MIT license, rather than as a hosted subscription service.
The main appeal is its combination of markup authoring and Ruby-side rendering features. Templates can include other templates and render partials, and embedding engines such as Markdown, Sass, and JavaScript extends what a view can express. A logic-less mode is also available through a plugin for teams that want to limit template logic. Rails streaming support is included, and integrations with Rails, Sinatra, Rack, and Tilt give Ruby developers several ways to fit Slim into an application stack.
Slim's focus is also its main trade-off: teams need to choose and maintain a specialized indentation-based syntax, and Ruby expressions and control flow may be a poor fit for projects seeking strictly logic-less templates. It is self-hosted, so it suits teams selecting a Ruby library for their own application rather than buyers looking for a managed template service. Choose Slim when concise Ruby templates, escaping, partials, and embedded engines are useful; consider another approach if conventional HTML syntax or a hosted product is a requirement.
Slim pros and cons
- Where it wins
- Indentation-based syntax avoids required closing tags.
- Escapes HTML by default and supports Ruby expressions and control flow.
- Works with Rails, Sinatra, Rack, and Tilt; supports partials and embedded engines.
- Where it doesn't
- Its specialized syntax may not suit teams preferring conventional HTML templates.
- Ruby expressions and control flow make it less suited to logic-less templating.
- It is a self-hosted library rather than a hosted subscription product.
Slim fact sheet, pricing and score →
Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.
Last updated · How we research and update