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. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the HTML Academy learning path, and your progress syncs across the web and the CoddyKit app. The HTML Academy course includes 4 lessons in total.
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.
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Frequently Asked Questions
Is the “Server-Side Templating Jinja2 Handlebars” lesson free?
Yes — any 3 lessons of the HTML Academy learning path, including “Server-Side Templating Jinja2 Handlebars”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The HTML Academy course includes 4 lessons in total.
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, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.
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