/Wiki/sources/honojs__hono/2026/https-hono-dev-llms-full-txt-header-ffd84c677deb-header-s0573-c0000.md
header() - hono-docs
header() Source evidence: /Sources/raw/honojs hono/honojs hono.md Canonical citation: https://hono.dev/llms full.txt header Summary Get the request header va...
header()
Source evidence: /Sources/raw/honojshono/honojshono.md Canonical citation: https://hono.dev/llms-full.txt#header
Summary
Get the request header value. ts twoslash import { Hono } from 'hono' const app = new Hono() // ---cut--- app.get('/', (c) => { const userAgent = c.req.header('User-Agent') // ^? return c.text(`Your user agent is ${userAgent}`) }) ...
Content
Get the request header value.
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/', (c) => {
const userAgent = c.req.header('User-Agent')
// ^?
return c.text(`Your user agent is ${userAgent}`)
})::: warning
When c.req.header() is called with no arguments, all keys in the returned record are lowercase.
If you want to get the value of a header with an uppercase name,
use c.req.header(“X-Foo”).
// ❌ Will not work
const headerRecord = c.req.header()
const foo = headerRecord['X-Foo']
// ✅ Will work
const foo = c.req.header('X-Foo'):::
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