Req.params vs req.query vs req.body in Express: Key Differences and Usage

In Express, req.params holds route parameters from the URL path, req.query contains URL query string parameters, and req.body carries data sent in the request body, usually from POST or PUT requests. Each serves a different purpose for accessing client-sent data in HTTP requests.

Quick Comparison

Here is a quick table comparing req.params, req.query, and req.body in Express:

Feature	req.params	req.query	req.body
Source	URL path segments defined in route	URL query string after ?	HTTP request body content
Typical HTTP Methods	GET, POST, PUT, DELETE (in URL)	GET (usually)	POST, PUT, PATCH
Data Format	String values from URL	String values from URL	Usually JSON, form data, or text
Use Case	Identify resource by ID or name in URL	Filter or sort data via URL	Send complex data like forms or JSON
Access Example	/user/:id → req.params.id	/search?term=js → req.query.term	JSON body → req.body object

Key Differences

req.params contains values extracted from the URL path defined by route parameters. For example, in a route like /user/:id, the id part is a parameter accessible via req.params.id. This is useful for identifying specific resources.

req.query holds key-value pairs from the URL query string, which comes after the ? in a URL. These are typically used for filtering, sorting, or searching, like /products?category=books. The values are always strings.

req.body contains data sent in the request body, usually with POST, PUT, or PATCH requests. This data can be JSON, form data, or other formats and requires middleware like express.json() to parse. It is used for sending complex or large data from the client to the server.

Code Comparison

javascript

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

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

app.listen(3000, () => console.log('Server running on port 3000'));

Output

If you visit http://localhost:3000/user/123, the response will be: User ID from req.params: 123

req.query Equivalent

javascript

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

app.get('/search', (req, res) => {
  res.send(`Search term from req.query: ${req.query.term}`);
});

app.listen(3000, () => console.log('Server running on port 3000'));

Output

If you visit http://localhost:3000/search?term=express, the response will be: Search term from req.query: express

When to Use Which

Choose req.params when you need to capture specific parts of the URL path, like IDs or names that identify a resource.

Choose req.query when you want to accept optional filters, sorting options, or search terms via the URL query string.

Choose req.body when the client sends data in the request body, such as form submissions or JSON payloads, typically in POST or PUT requests.

Key Takeaways

req.params extracts dynamic segments from the URL path.

req.query reads key-value pairs from the URL query string.

req.body holds data sent in the request body, often JSON or form data.

Use req.params for resource identification, req.query for filtering, and req.body for sending complex data.

Middleware like express.json() is needed to parse req.body.