How to Get Query String in Express: Simple Guide

In Express, you get the query string parameters from the req.query object inside your route handler. This object contains key-value pairs of the query parameters sent in the URL after the ? symbol.

Syntax

Use req.query inside your route handler to access query parameters. It returns an object where each key is a parameter name and the value is the parameter value as a string.

• req: The request object from Express.
• query: Property holding query parameters as an object.

javascript

app.get('/path', (req, res) => {
  const queryParams = req.query;
  res.send(queryParams);
});

Example

This example shows a simple Express server that reads query parameters from the URL and sends them back as JSON.

javascript

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

app.get('/search', (req, res) => {
  const queries = req.query;
  res.json({ receivedQueries: queries });
});

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

Output

Server running at http://localhost:3000

When you visit: http://localhost:3000/search?term=books&sort=asc
Response JSON: {"receivedQueries":{"term":"books","sort":"asc"}}

Common Pitfalls

Common mistakes when getting query strings in Express include:

• Trying to parse req.url manually instead of using req.query.
• Expecting query parameters to be automatically converted to numbers or booleans (they are always strings).
• Not handling missing or undefined query parameters, which can cause errors if you assume they exist.

Always check if a query parameter exists before using it.

javascript

app.get('/example', (req, res) => {
  // Wrong: manually parsing URL string
  // const url = req.url;
  // const queryString = url.split('?')[1];

  // Right: use req.query
  const page = req.query.page || '1'; // default to '1' if missing
  res.send(`Page number is ${page}`);
});

Quick Reference

Summary tips for getting query strings in Express:

• Use req.query to get query parameters as an object.
• Query values are always strings; convert them if needed.
• Check for undefined parameters before using them.
• Express parses query strings automatically; no extra parsing needed.

Key Takeaways

Access query parameters in Express using the req.query object inside route handlers.

Query parameters are strings; convert them explicitly if you need numbers or booleans.

Always check if a query parameter exists before using it to avoid errors.

Express automatically parses the query string; manual parsing is unnecessary.

Use default values to handle missing query parameters gracefully.