ERB
ERB: A free Ruby library for evaluating template tags and generating strings. Ranked #12 of 65 in Template Engine Software by our editors (8.3/10); pricing: Free plan; best for ruby developers embedding Ruby in templates.
At a glance
- Editor score8.3 / 10
- PricingFree plan
- Best forRuby developers embedding Ruby in templates
- Free planYes
- Paid fromFree
- Facts checked23 Oct 2026
Where it wins
- Processes Ruby expressions, executable code, and comment tags in templates
- Bindings expose local variables and constants to templates
- Supports encoding settings and configurable whitespace trimming
Where it doesn't
- Focused on Ruby rather than templates for other programming languages
- Templates can execute Ruby code, so they are not just declarative markup
- A developer library, not a hosted template service
Our verdict on ERB
ERB is a template processor included in Ruby’s standard library. It takes plain-text templates with Ruby expression tags, executable code, and comments, then evaluates the resulting Ruby code to produce a string. That makes it a fit for Ruby developers who want to generate text from templates within Ruby applications or scripts, including plain text and HTML. It is a developer library, not a hosted service.
The central capability is embedding Ruby directly in a template. A supplied binding lets a template access local variables and constants, while templates can also define methods, modules, and classes. This gives ERB a code-generation syntax model and room for logic beyond simple value insertion. It also means ERB is best suited to teams already comfortable placing executable Ruby in templates; developers seeking a language-neutral or strictly declarative template format should consider a different engine.
ERB is free and open source, and is distributed under Ruby’s free-software licensing terms. It is self-hosted as part of the Ruby development environment rather than offered as a hosted service. Encoding controls and configurable whitespace trimming address output-formatting needs, but ERB’s focus remains Ruby template processing. Choose it when Ruby integration and direct access to Ruby values matter more than a broad cross-language feature set; look elsewhere if the project needs a hosted workflow or templates independent of Ruby.
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ERB pricing
ERB fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Rendering mode | Not verified |
| Syntax model | Code-generation |
| Template inheritance | Not verified |
| Automatic escaping | Not verified |
| Sandbox mode | Not verified |
| Async rendering | Not verified |
| License model | Open-source |
| Deployment | Self-hosted |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan |
| Website | docs.ruby-lang.org |
| Facts checked | 23 Oct 2026 |
Alternatives to ERB
- JinjaJinja gives Python applications inheritance, configurable rendering, and compilation in an open-source engine.9.4
- TwigA free, open-source PHP engine for compiled templates, inheritance, escaping, and sandboxing.9.3
- Handlebars.jsA free, open-source template engine for JavaScript projects that need reusable HTML.9.2
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The editor score above is our own research. What this page doesn't have yet is a reader's view — what you used ERB for, what worked and what didn't. No stars are seeded and no review is paid for; an editor reads every one before it appears.
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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