Request & response

What you read from the request, how bodies are parsed, and how responses carry types.

Request

Property	Notes
`url`	Normalized pathname
`method`	HTTP method enum
`headers`	Native `Headers`
`body`	Parsed body (schema type, else `unknown`)
`query`	Query params; schema type or `Record<string, string \| undefined>`
`params`	Route params; inferred from the URL or schema
`cookies`	Parsed `Cookie` header, URI-decoded
`ip`	Client IP, or `null`
`data`	Context filled by middlewares
`raw`	Original `Request`

Fill req.data key by key (req.data.user = user). Replacing the object drops keys added upstream.

query, params, and cookies are read-only. You write to data and body.

Body parsing

Parsed from Content-Type. GET never gets a body. Malformed bodies yield null rather than throwing.

Content-Type	req.body
application/json	Parsed JSON
multipart/form-data	Object of fields; files as Web `File`
application/x-www-form-urlencoded	Object of string fields
anything else	Raw text

For uploads, validation with z.file(), and sendFile, see Files.

Cookies

If the request has a Cookie header, each name=value pair is stored in req.cookies. Values are passed through decodeURIComponent; if decoding fails, the raw value is kept.

.get("/me", (req, res) => {
  const session = req.cookies.session;
  return res.json({ session: session ?? null });
})

ExpressAPI reads cookies; it does not set Set-Cookie for you. Use res.setHeader("Set-Cookie", ...) when you need to write them.

Response

res.json({ message: "Success" });           // 200 JSON (typed for the client)
res.status(201).json({ created: true });  // custom status
res.send("Plain text");                   // raw body
res.redirect("/new-location", 301);       // redirect (default 307)
await res.sendFile("/path/to/file.pdf");  // stream a file
res.type("xml").send("<root></root>");    // Content-Type from extension
res.setHeader("X-Custom", "value").json({});

res.json() returns TypedResponse<T> - that phantom type is what HttpClient reads
send / redirect / sendFile return a plain Response and contribute no type information
type(ext) maps an extension (e.g. "json", "pdf") to a MIME type via @std/media-types
size(n) sets Content-Length