Templ

templ is a language, CLI, and runtime for building HTML UIs in Go. You write .templ files, run templ generate, and get ordinary Go functions that render type-safe HTML. Current line: v0.3.x. Requires Go 1.24+.

Overview

• What: HTML components compiled to plain Go functions
• Install: go install github.com/a-h/templ/cmd/templ@latest
• Workflow: write hello.templ -> templ generate -> hello_templ.go -> call it like any Go function
• Core type: templ.Component, a one-method interface: Render(ctx context.Context, w io.Writer) error
• Escaping: expression output is HTML-escaped automatically
• Interactivity: pairs with htmx or Datastar via fragment rendering; no client runtime of its own
• Deploy: a plain Go binary or a small distroless container

Why templ

Go’s html/template gives you strings with holes, parsed at runtime. templ gives you functions: components take typed arguments, and wrong argument types fail at build time, not on the first request.

templ greeting(name string) {
    <p>Hello, { name }</p>
}

// generated by templ generate
func greeting(name string) templ.Component

Because Render writes to any io.Writer, the same component can serve an HTTP response, write a static file, or render into a test buffer. templ is deliberately small: no router, no asset pipeline, no client runtime. You bring the Go stdlib plus whatever else you already use.

Good fit: server-rendered sites and apps shipped as a single Go binary, HTML-over-the-wire UIs with htmx, embedded admin panels.

Poor fit: heavy client-side SPAs that need a large JavaScript component ecosystem.

Contents

• Concepts
  • Components and Syntax - component model, expressions, control flow, composition, templ.Join/KV/Once/Raw
  • Rendering Model - the generate pipeline, Component interface, Handler options, streaming
  • Security and Scripts - auto-escaping, script templates, JSONScript
• Quickstart
  • First App - install, generate, and serve a first component
• How-To
  • Use with htmx - hx-* attributes and native fragment rendering
  • Style with Tailwind - class attributes, LSP setup, css components
  • Cache Rendered Pages - roll-your-own page cache and Cache-Control
  • Deploy in Docker - multi-stage distroless image, static assets
• Deep-Dives
  • Generated Code - what *_templ.go contains and why it matters
• Troubleshooting
  • Common Errors - error catalog with causes and fixes
• Notes
  • Ecosystem - component libraries, interactivity, tooling

Resources

• templ.guide - official documentation
• a-h/templ - source repository