How to Return HTML in Flask: Simple Guide with Examples

In Flask, you can return HTML by using the render_template function to serve HTML files from a templates folder or by returning a raw HTML string directly from a route function. The render_template method is preferred for larger HTML content and better organization.

Syntax

To return HTML in Flask, you typically use the render_template function or return a string containing HTML directly.

• render_template('filename.html'): Renders an HTML file from the templates folder.
• Returning a string: You can return raw HTML as a string directly from a route.

python

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def home():
    # Return HTML file
    return render_template('index.html')

@app.route('/raw')
def raw_html():
    # Return raw HTML string
    return '<h1>Hello, Flask!</h1><p>This is raw HTML.</p>'

Example

This example shows a Flask app returning HTML using both render_template and a raw HTML string. The templates/index.html file contains simple HTML content.

python

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def home():
    return render_template('index.html')

@app.route('/raw')
def raw_html():
    return '<h1>Hello, Flask!</h1><p>This is raw HTML returned directly.</p>'

if __name__ == '__main__':
    app.run(debug=True)

Output

When you visit http://localhost:5000/, the browser shows the HTML from index.html file.
When you visit http://localhost:5000/raw, the browser shows the raw HTML string content.

Common Pitfalls

• Not placing HTML files inside a folder named templates causes render_template to fail.
• Returning raw HTML strings is okay for small snippets but hard to maintain for bigger pages.
• Forgetting to import render_template from Flask leads to errors.
• Not running the Flask app with debug=True during development can make debugging harder.

python

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    # Wrong: render_template not imported
    # return render_template('index.html')  # This will cause an error
    # Right way:
    return '<h1>Fallback HTML</h1>'

Quick Reference

Summary tips for returning HTML in Flask:

• Use render_template for HTML files stored in templates/.
• Return raw HTML strings for very simple responses.
• Keep HTML files organized in the templates folder.
• Always import render_template when using it.
• Run Flask with debug=True during development for easier error tracking.

Key Takeaways

Use render_template to return HTML files from the templates folder in Flask.

You can return raw HTML strings directly for simple responses.

Always place HTML files inside a folder named templates.

Import render_template from flask to avoid errors.

Run Flask with debug=True during development for easier debugging.