How to Get Route Params in Express: Simple Guide

In Express, you get route parameters using req.params. Define parameters in your route path with a colon, like /user/:id, then access the value with req.params.id inside your route handler.

Syntax

Route parameters are defined in the route path using a colon : followed by the parameter name. Inside the route handler, you access these parameters via req.params, which is an object containing key-value pairs of parameter names and their values.

• /path/:paramName defines a route parameter named paramName.
• req.params.paramName accesses the value of that parameter.

javascript

app.get('/user/:id', (req, res) => {
  const userId = req.params.id;
  res.send(`User ID is ${userId}`);
});

Example

This example shows a simple Express server with a route that captures a user ID from the URL and sends it back in the response.

javascript

import express from 'express';
const app = express();
const port = 3000;

app.get('/user/:id', (req, res) => {
  const userId = req.params.id;
  res.send(`User ID is ${userId}`);
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

Output

Server running at http://localhost:3000

// When you visit http://localhost:3000/user/123
// The response will be: User ID is 123

Common Pitfalls

Common mistakes when using route params include:

• Forgetting the colon : before the parameter name in the route path.
• Trying to access parameters from req.query or req.body instead of req.params.
• Not matching the route path exactly, causing the route not to trigger.

Here is an example of a wrong and right way:

javascript

// Wrong: Missing colon in route path
app.get('/user/id', (req, res) => {
  // req.params.id will be undefined
  res.send(`User ID is ${req.params.id}`);
});

// Right: Colon before parameter name
app.get('/user/:id', (req, res) => {
  res.send(`User ID is ${req.params.id}`);
});

Quick Reference

Concept	Usage	Description
Define param	/path/:param	Use colon before param name in route path
Access param	req.params.param	Get value of param inside route handler
Multiple params	/user/:id/book/:bookId	Access with req.params.id and req.params.bookId
No colon	/user/id	No param, 'id' is literal part of path

Key Takeaways

Use a colon before the parameter name in the route path to define route params.

Access route parameters inside handlers with req.params.paramName.

Route parameters are part of the URL path, not query strings or body data.

Always match the route path exactly to capture parameters correctly.

You can define multiple route parameters in one path and access each via req.params.