Route Params vs Query Params vs Body in Express

Route Params vs Query Params vs Body in Express

Express gives you three ways to read data from a request: params, query, and body. Here is when to use each.

Route Params

Used to identify a specific resource. Part of the URL path.

GET /users/:id
req.params.id

Use for: identifying a single resource (a user id, a post id). Always a string. Convert to ObjectId or number when needed.

Query Params

Used for optional filters and options. After the ? in the URL.

GET /users?role=admin&limit=10
req.query.role, req.query.limit

Use for: filtering, sorting, pagination, optional fields. Always strings. Coerce when needed.

Body

Used for the data you are sending to create or update a resource. Sent in the request body (usually JSON).

POST /users { "name": "Kunal", "email": "[email protected]" }
req.body.name, req.body.email

Use for: POST and PATCH bodies. Requires express.json middleware. The body can be large and complex.

Comparison

When to Use Each

• Route params: when the data identifies a resource. /users/:id. Required.
• Query params: when the data is optional filters. /users?role=admin. Optional.
• Body: when the data is large or complex, or you are creating/updating. POST /users with body.

Common Mistakes

• Putting IDs in query params (should be in path).
• Putting filters in the body of a GET request (GET should not have a body).
• Forgetting to add express.json, so req.body is undefined.

The Takeaway

Route params identify a resource (in path, required). Query params filter (after ?, optional). Body sends data for create/update (with express.json, larger). Use the right one for the right job. Do not put IDs in query params or filters in body.