Server-Side Templating Jinja2 Handlebars
Use template engines to render HTML dynamically on the server.
Server-Side Templating Jinja2 Handlebars is a free HTML Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the HTML Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Server-Side Templating?
Server-side templates generate HTML on the server before sending to the browser. They give SEO-friendly markup on first byte, work without JavaScript, and avoid the "blank page until JS loads" problem of pure client-side rendering.
Jinja2 (Python)
Jinja2 is the de facto Python templating library — used by Flask, Django (via included or jinja2 backend), Pelican, mkdocs. Logic in {% %} tags, expressions in {{ }}: <h1>{{ title }}</h1> for variables, {% for item in items %} for loops.
<ul>
{% for item in items %}
<li>{{ item.name }} — ${{ item.price }}</li>
{% endfor %}
</ul>Handlebars (JavaScript)
Handlebars is the most-used Node.js templating library, popular for transactional emails (SendGrid, Mailgun) and SSR via Express. Expressions in {{ }}, blocks via {{# }}: {{#each items}}<li>{{name}}</li>{{/each}}.
<ul>
{{#each items}}
<li>{{name}} — ${{price}}</li>
{{/each}}
</ul>Auto-Escaping
Both engines auto-escape variable output by default — {{ user.name }} with name = "<script>" outputs "<script>", neutralizing XSS. Always rely on auto-escape; use the explicit raw filter (Jinja: {{ x|safe }}, Handlebars: {{{x}}}) only for trusted HTML.
Template Inheritance
Jinja: {% extends "base.html" %} in child plus {% block content %}{% endblock %} in base. Handlebars: {{#> layout }}{{/layout}} with partial blocks. Lets a base layout define structure once; pages fill in the variable regions.
Includes and Partials
Jinja: {% include "header.html" %}. Handlebars: {{> header}}. Both inline another template into the current one. Partials are the building blocks of large component libraries — composed into pages and layouts.
Filters and Helpers
Jinja filters: {{ price|currency }}. Handlebars helpers: {{currency price}}. Both let you call formatting functions on values. Define your own for project-specific transformations (date formatting, pluralization, link building).
Conditionals
Jinja: {% if user.is_logged_in %}Welcome{% else %}Sign in{% endif %}. Handlebars: {{#if user.isLoggedIn}}Welcome{{else}}Sign in{{/if}}. Branch templates by data without resorting to client-side JS to hide/show content.
Performance
Both engines pre-compile templates to functions, then call those functions per request. Compilation is one-time; rendering is fast. For very high-traffic sites, cache rendered output at the edge (Varnish, Cloudflare) rather than re-rendering identical pages.
Localization
Combine templates with i18n libraries: Jinja2 + Babel for Python, Handlebars + i18next for Node. Templates carry translation keys ({{ t "welcome" }}); the i18n layer resolves to the right language. Lets one template render in many languages.
Framework Templates
Modern frameworks bring their own template formats: ERB (Rails), Twig (Symfony), Blade (Laravel), Razor (.NET), Slim/Haml (more terse). The patterns are the same; the syntax differs. Pick the engine that matches your backend language and ecosystem.
Migrating Toward Components
Templates work great for traditional server-rendered sites. For more interactive apps, frameworks like Next.js (React), Nuxt (Vue) and SvelteKit blur the line — they render templates on the server but the same components hydrate on the client for interactivity.
Knowledge Check
Why is auto-escaping the default behavior in templating engines like Jinja2 and Handlebars?
Summary
Server-side templating engines (Jinja2 for Python, Handlebars for JS, ERB/Twig/Blade for other stacks) generate HTML on the server with variables, loops, conditionals, partials and inheritance. Auto-escaping defends against XSS by default. Pair with i18n libraries for multi-language sites. Templates are the foundation; modern frameworks layer hydration on top.
Frequently asked questions
Is the “Server-Side Templating Jinja2 Handlebars” lesson free?
Yes — the full text of “Server-Side Templating Jinja2 Handlebars” is free to read here on the web, and the HTML Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the HTML Academy course, upgrade to CoddyKit PRO.
What will I learn in “Server-Side Templating Jinja2 Handlebars”?
Use template engines to render HTML dynamically on the server. You practise HTML Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start HTML Academy?
No prior experience is required. HTML Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Server-Side Templating Jinja2 Handlebars” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this HTML Academy lesson?
Yes. Every HTML Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Component Extraction and Partials
- Server-Side Templating Jinja2 Handlebars
- HTML in Design Systems
- Documentation and Styleguide Integration