`ctx.response.type`

Gets or sets the `Content-Type` response header using MIME types or file extensions.

Syntax

ctx.response.type = type  // or ctx.type = type

Parameters

Name	Type	Required	Description
`type`	`string`	Yes	A MIME type string (`"application/json"`) or a file extension without the dot (`"json"`, `"html"`, `"png"`). Koa resolves the extension to a MIME type via the `mime-types` package.

Returns

string — The current Content-Type without parameters (e.g. `"application/json"`).

Examples

import Koa from 'koa';

const app = new Koa();

app.use(async (ctx) => {
  ctx.type = 'html';
  ctx.body = '<h1>Hello Koa</h1>';
});

app.listen(3000);

Output

Content-Type: text/html; charset=utf-8

app.use(async (ctx) => {
  ctx.type = 'application/pdf';
  ctx.body = pdfBuffer;
});

Output

Content-Type: application/pdf

Notes

When you assign an object or array to `ctx.body`, Koa automatically sets `Content-Type` to `application/json`. For strings it defaults to `text/html` if the string contains a `<` character, otherwise `text/plain`. Manually setting `ctx.type` overrides the inferred type.