Templ

An HTML templating language for Go that has great developer tooling.

Source (GitHub)

Templ is an open-source, code-generation-based, type-safe HTML templating framework for Go. Its main goal is to eliminate the risk of runtime template errors by making use of Go’s compile-time checks and to provide a convenient DSL (Domain Specific Language) for writing dynamic user interfaces. 1 2

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History

Templ was created by Andrew Hood (GitHub: @a-h) around 2019–2020 1, 3. He sought a templating solution that was both idiomatic to Go and type-safe, circumventing the runtime-only checks commonly found in text/template or html/template.

Templ emerged as a side project and evolved through community contributions. Early commits date back to November 2019 4. It’s licensed under the MIT license 1.

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Key Characteristics

1. Type-Safe Templating

   • Compile-Time Validation: Templates are turned into Go code, catching type errors at build time 1, 2.
   • No Reflection: Templ does not rely on runtime reflection, improving reliability and performance 1.

2. Code Generation

   • Templ’s DSL: Templ uses .templ files that resemble HTML with inline Go expressions. The CLI translates them into .go files 2, 5.
   • Minimal Overhead: The generated code is idiomatic Go with no large runtime dependencies 1.

3. Modular Architecture

   • Partial Templates: Allows for smaller reusable components.
   • Layouts: Shared layouts or “master pages” can wrap child templates 1, 2.

4. Integration

   • Standard Library: Generated functions integrate easily with net/http 1, [2].
   • Go Web Frameworks: Works with Gin, Echo, or any router because you just call the compiled function 2.

5. Open Source & Community-Driven

   • MIT License: Free to use in personal or commercial projects 1.
   • Community Contributions: Pull requests, issue discussions, and examples on GitHub 3.

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How Templ Works

1. Write Templ DSL:
   A .templ file uses HTML-like syntax with embedded Go expressions:

   Template MyTemplate(person Person) {
     div {
       h1("Hello, " + person.Name)
       if person.Age > 18 {
         p("You are an adult.")
       } else {
         p("You are a minor.")
       }
     }
   }

2. Run Templ CLI:

   templ generate

   This generates .go files with strongly typed functions 2, 5.

3. Import & Render:

   func handler(w http.ResponseWriter, r *http.Request) {
       myTemplate := MyTemplate(Person{Name: "Alice", Age: 25})
       w.Write([]byte(myTemplate))
   }

   The rendered output is pure HTML 5.

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Pros

1. Compile-Time Safety

   • Prevents runtime template surprises via immediate feedback during compilation 1.

2. Performance

   • No runtime parsing overhead; the output is directly compiled Go 1, 5.

3. Developer Experience

   • DSL is HTML-like with embedded Go logic, reminiscent of JSX or Razor pages 1, 2.

4. Flexible Integration

   • Easily integrates with net/http or any Go router or framework 2, 3.

5. Lightweight

   • Everything compiles into your Go binary with no additional templating engines or runtime interpreters 1.

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Cons

1. Learning Curve

   • Requires adopting the DSL and an extra build step via templ generate 1, 2.

2. Limited Ecosystem

   • Official html/template has broader adoption and community resources; Templ is still growing 1, 3.

3. Increased Build Complexity

   • A code generation phase means CI/CD pipelines must run templ generate before compiling 2.

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Use Cases

• Server-Side Web Rendering: A type-safe alternative to html/template for building server-rendered UIs 1, [5].
• Email Template Generation: Avoid runtime issues when generating HTML email content 1, 2.
• Microservices / Small UIs: Ideal for mini web interfaces in microservices 2.
• Reusable UI Components: Build partials and layouts that can be composed into larger pages 5.

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Getting Started

Installation

go install github.com/a-h/templ/cmd/templ@latest

Installs the Templ CLI tool into $GOPATH/bin 2.

Project Structure

myproject/
├── main.go
└── templates/
    └── index.templ

A common folder layout for Templ-based projects 2, 5.

Write Your First Templ (index.templ)

Template Index(name string) {
  html {
    head {
      title("Welcome!")
    }
    body {
      h1("Hello " + name)
    }
  }
}

A basic example that uses Templ’s DSL 2, 5.

Generate & Build

templ generate
go build .

Templ CLI creates index_templ.go that you can compile alongside your Go code 2.

Use the Generated Code in main.go

package main

import (
    "log"
    "net/http"

    "myproject/templates" // The generated file
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        output := templates.Index("Alice")
        w.Write([]byte(output))
    })
    log.Fatal(http.ListenAndServe(":8080", nil))
}

A standard approach using Templ in a Go application 2, 5.

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Learning Resources

• Official GitHub Repository
  https://github.com/a-h/templ
  Read the README and explore the code.

  Source: 1

• Templ Wiki / Docs
  Templ Wiki
  Contains official guides, advanced usage, and examples.

  Source: 2

• Example Projects
  Examples Folder
  Real-world code samples.

  Source: 5

• Community Articles / Tutorials

  • Search Medium or dev.to for Templ tutorials.
  • Community blog posts often linked in Discussions.

  Source: 3

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Media Resources

• Community Screencasts
  Check the “Discussions” section or pinned issues on GitHub for user-created video tutorials or demos.

(Templ doesn’t yet have official YouTube presence like Go does, but user-made content is emerging.)

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Sources

1. Templ GitHub Repository - README
   • Official README with an introduction, high-level overview, and basic instructions.
2. Templ Wiki
   • Official documentation covering usage patterns, “getting started,” advanced configuration, partials, layouts, etc.
3. Templ GitHub Discussions
   • Community Q&A, announcements, and knowledge sharing.
4. Templ Initial Commits History
   • Shows some of the earliest code, indicating the timeline (circa late 2019).
5. Templ Examples Folder
   • Contains actual code samples for reference, from simple “Hello World” to more complex partial/layout usage.

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