expressurlencoded

express.urlencoded is a built-in middleware function in Express.js that parses incoming requests with URL-encoded payloads (the standard content type for form submissions: application/x-www-form-urlencoded). It is effectively a wrapper around body-parser’s urlencoded parser and is available in Express 4 and later. When enabled, it reads the request body and populates req.body with a key-value object representing the form data. It only handles requests with a matching content type.

Usage typically involves mounting the middleware near the top of an Express app. For example: app.use(express.urlencoded({ extended: true })); This allows forms submitted via POST (and similar methods) to populate req.body. If a form sends { username: "alice", age: "30" }, req.body will be { username: "alice", age: "30" }.

Options control how parsing is performed. extended controls whether to use the qs library for parsing nested objects and arrays (true) or the native querystring library (false). Other common options include limit (maximum body size), type (content-type to parse, defaults to application/x-www-form-urlencoded), parameterLimit (maximum number of parameters), inflate (whether to allow compressed bodies), and verify (a function invoked with the raw buffer before parsing). By combining these options, developers can tailor how URL-encoded form data is accepted and transformed.

Express.urlencoded is used in conjunction with other body-parsing middleware, such as express.json(), to handle different request payloads. It does not parse JSON payloads.