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Typed utilities for parsing, manipulating, and serializing HTTP header values. headers provides focused classes for common HTTP headers.

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Features

  • Header-Specific Classes - Purpose-built APIs for Accept, Cache-Control, Content-Type, and more
  • Round-Trip Safety - Parse from raw values and serialize back with .toString()
  • Typed Operations - Work with structured values instead of manual string parsing

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Installation

npm i remix

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Supported Headers

Each supported header has a class that represents the header value. Use the static from() method to parse header values. Each class has a toString() method that returns the header value as a string.

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Accept

Parse, manipulate and stringify Accept headers. Implements Map<mediaType, quality>. 
import { Accept } from 'remix/headers'

// Parse from headers
let accept = Accept.from(request.headers.get('accept'))

accept.mediaTypes // ['text/html', 'text/*']
accept.weights // [1, 0.9]
accept.accepts('text/html') // true
accept.accepts('text/plain') // true (matches text/*)
accept.accepts('image/jpeg') // false
accept.getWeight('text/plain') // 1 (matches text/*)
accept.getPreferred(['text/html', 'text/plain']) // 'text/html'

// Iterate
for (let [mediaType, quality] of accept) {
  // ...
}

// Modify and set header
accept.set('application/json', 0.8)
accept.delete('text/*')
headers.set('Accept', accept)

// Construct directly
new Accept('text/html, text/*;q=0.9')
new Accept({ 'text/html': 1, 'text/*': 0.9 })
new Accept(['text/html', ['text/*', 0.9]])

// Use class for type safety when setting Headers values
let headers = new Headers({
  Accept: new Accept({ 'text/html': 1, 'application/json': 0.8 }),
})

​
Accept-Encoding

Parse, manipulate and stringify Accept-Encoding headers. Implements Map<encoding, quality>. 
import { AcceptEncoding } from 'remix/headers'

// Parse from headers
let acceptEncoding = AcceptEncoding.from(request.headers.get('accept-encoding'))

acceptEncoding.encodings // ['gzip', 'deflate']
acceptEncoding.weights // [1, 0.8]
acceptEncoding.accepts('gzip') // true
acceptEncoding.accepts('br') // false
acceptEncoding.getWeight('gzip') // 1
acceptEncoding.getPreferred(['gzip', 'deflate', 'br']) // 'gzip'

// Modify and set header
acceptEncoding.set('br', 1)
acceptEncoding.delete('deflate')
headers.set('Accept-Encoding', acceptEncoding)

// Construct directly
new AcceptEncoding('gzip, deflate;q=0.8')
new AcceptEncoding({ gzip: 1, deflate: 0.8 })

​
Accept-Language

Parse, manipulate and stringify Accept-Language headers. Implements Map<language, quality>. 
import { AcceptLanguage } from 'remix/headers'

// Parse from headers
let acceptLanguage = AcceptLanguage.from(request.headers.get('accept-language'))

acceptLanguage.languages // ['en-us', 'en']
acceptLanguage.weights // [1, 0.9]
acceptLanguage.accepts('en-US') // true
acceptLanguage.accepts('en-GB') // true (matches en)
acceptLanguage.getWeight('en-GB') // 1 (matches en)
acceptLanguage.getPreferred(['en-US', 'en-GB', 'fr']) // 'en-US'

// Modify and set header
acceptLanguage.set('fr', 0.5)
acceptLanguage.delete('en')
headers.set('Accept-Language', acceptLanguage)

// Construct directly
new AcceptLanguage('en-US, en;q=0.9')
new AcceptLanguage({ 'en-US': 1, en: 0.9 })

​
Cache-Control

Parse, manipulate and stringify Cache-Control headers. 
import { CacheControl } from 'remix/headers'

// Parse from headers
let cacheControl = CacheControl.from(response.headers.get('cache-control'))

cacheControl.public // true
cacheControl.maxAge // 3600
cacheControl.sMaxage // 7200
cacheControl.noCache // undefined
cacheControl.noStore // undefined
cacheControl.noTransform // undefined
cacheControl.mustRevalidate // undefined
cacheControl.immutable // undefined

// Modify and set header
cacheControl.maxAge = 7200
cacheControl.immutable = true
headers.set('Cache-Control', cacheControl)

// Construct directly
new CacheControl('public, max-age=3600')
new CacheControl({ public: true, maxAge: 3600 })

​
Content-Disposition

Parse, manipulate and stringify Content-Disposition headers. 
import { ContentDisposition } from 'remix/headers'

// Parse from headers
let contentDisposition = ContentDisposition.from(
  response.headers.get('content-disposition')
)

contentDisposition.type // 'attachment'
contentDisposition.filename // 'example.pdf'
contentDisposition.filenameSplat // "UTF-8''%E4%BE%8B%E5%AD%90.pdf"
contentDisposition.preferredFilename // '例子.pdf' (decoded from filename*)

// Modify and set header
contentDisposition.filename = 'download.pdf'
headers.set('Content-Disposition', contentDisposition)

// Construct directly
new ContentDisposition('attachment; filename="example.pdf"')
new ContentDisposition({ type: 'attachment', filename: 'example.pdf' })

​
Content-Range

Parse, manipulate and stringify Content-Range headers. 
import { ContentRange } from 'remix/headers'

// Parse from headers
let contentRange = ContentRange.from(response.headers.get('content-range'))

contentRange.unit // "bytes"
contentRange.start // 200
contentRange.end // 1000
contentRange.size // 67589

// Unsatisfied range
let unsatisfied = ContentRange.from('bytes */67589')
unsatisfied.start // null
unsatisfied.end // null
unsatisfied.size // 67589

// Construct directly
new ContentRange({ unit: 'bytes', start: 0, end: 499, size: 1000 })

​
Content-Type

Parse, manipulate and stringify Content-Type headers. 
import { ContentType } from 'remix/headers'

// Parse from headers
let contentType = ContentType.from(request.headers.get('content-type'))

contentType.mediaType // "text/html"
contentType.charset // "utf-8"
contentType.boundary // undefined (or boundary string for multipart)

// Modify and set header
contentType.charset = 'iso-8859-1'
headers.set('Content-Type', contentType)

// Construct directly
new ContentType('text/html; charset=utf-8')
new ContentType({ mediaType: 'text/html', charset: 'utf-8' })
Parse, manipulate and stringify Cookie headers. Implements Map<name, value>. 
import { Cookie } from 'remix/headers'

// Parse from headers
let cookie = Cookie.from(request.headers.get('cookie'))

cookie.get('session_id') // 'abc123'
cookie.get('theme') // 'dark'
cookie.has('session_id') // true
cookie.size // 2

// Iterate
for (let [name, value] of cookie) {
  // ...
}

// Modify and set header
cookie.set('theme', 'light')
cookie.delete('session_id')
headers.set('Cookie', cookie)

// Construct directly
new Cookie('session_id=abc123; theme=dark')
new Cookie({ session_id: 'abc123', theme: 'dark' })
new Cookie([
  ['session_id', 'abc123'],
  ['theme', 'dark'],
])

​
If-Match

Parse, manipulate and stringify If-Match headers. Implements Set<etag>. 
import { IfMatch } from 'remix/headers'

// Parse from headers
let ifMatch = IfMatch.from(request.headers.get('if-match'))

ifMatch.tags // ['"67ab43"', '"54ed21"']
ifMatch.has('"67ab43"') // true
ifMatch.matches('"67ab43"') // true (checks precondition)
ifMatch.matches('"abc123"') // false

// Note: Uses strong comparison only (weak ETags never match)
let weak = IfMatch.from('W/"67ab43"')
weak.matches('W/"67ab43"') // false

// Modify and set header
ifMatch.add('"newetag"')
ifMatch.delete('"67ab43"')
headers.set('If-Match', ifMatch)

// Construct directly
new IfMatch(['abc123', 'def456'])

​
If-None-Match

Parse, manipulate and stringify If-None-Match headers. Implements Set<etag>. 
import { IfNoneMatch } from 'remix/headers'

// Parse from headers
let ifNoneMatch = IfNoneMatch.from(request.headers.get('if-none-match'))

ifNoneMatch.tags // ['"67ab43"', '"54ed21"']
ifNoneMatch.has('"67ab43"') // true
ifNoneMatch.matches('"67ab43"') // true

// Supports weak comparison (unlike If-Match)
let weak = IfNoneMatch.from('W/"67ab43"')
weak.matches('W/"67ab43"') // true

// Modify and set header
ifNoneMatch.add('"newetag"')
ifNoneMatch.delete('"67ab43"')
headers.set('If-None-Match', ifNoneMatch)

// Construct directly
new IfNoneMatch(['abc123'])

​
If-Range

Parse, manipulate and stringify If-Range headers. 
import { IfRange } from 'remix/headers'

// Parse from headers
let ifRange = IfRange.from(request.headers.get('if-range'))

// With HTTP date
ifRange.matches({ lastModified: 1609459200000 }) // true
ifRange.matches({ lastModified: new Date('2021-01-01') }) // true

// With ETag
let etagHeader = IfRange.from('"67ab43"')
etagHeader.matches({ etag: '"67ab43"' }) // true

// Empty/null returns empty instance (range proceeds unconditionally)
let empty = IfRange.from(null)
empty.matches({ etag: '"any"' }) // true

// Construct directly
new IfRange('"abc123"')

​
Range

Parse, manipulate and stringify Range headers. 
import { Range } from 'remix/headers'

// Parse from headers
let range = Range.from(request.headers.get('range'))

range.unit // "bytes"
range.ranges // [{ start: 200, end: 1000 }]
range.canSatisfy(2000) // true
range.canSatisfy(500) // false
range.normalize(2000) // [{ start: 200, end: 1000 }]

// Multiple ranges
let multi = Range.from('bytes=0-499, 1000-1499')
multi.ranges.length // 2

// Suffix range (last N bytes)
let suffix = Range.from('bytes=-500')
suffix.normalize(2000) // [{ start: 1500, end: 1999 }]

// Construct directly
new Range({ unit: 'bytes', ranges: [{ start: 0, end: 999 }] })
Parse, manipulate and stringify Set-Cookie headers. 
import { SetCookie } from 'remix/headers'

// Parse from headers
let setCookie = SetCookie.from(response.headers.get('set-cookie'))

setCookie.name // "session_id"
setCookie.value // "abc"
setCookie.path // "/"
setCookie.httpOnly // true
setCookie.secure // true
setCookie.domain // undefined
setCookie.maxAge // undefined
setCookie.expires // undefined
setCookie.sameSite // undefined

// Modify and set header
setCookie.maxAge = 3600
setCookie.sameSite = 'Strict'
headers.set('Set-Cookie', setCookie)

// Construct directly
new SetCookie('session_id=abc; Path=/; HttpOnly; Secure')
new SetCookie({
  name: 'session_id',
  value: 'abc',
  path: '/',
  httpOnly: true,
  secure: true,
})

​
Vary

Parse, manipulate and stringify Vary headers. Implements Set<headerName>. 
import { Vary } from 'remix/headers'

// Parse from headers
let vary = Vary.from(response.headers.get('vary'))

vary.headerNames // ['accept-encoding', 'accept-language']
vary.has('Accept-Encoding') // true (case-insensitive)
vary.size // 2

// Modify and set header
vary.add('User-Agent')
vary.delete('Accept-Language')
headers.set('Vary', vary)

// Construct directly
new Vary('Accept-Encoding, Accept-Language')
new Vary(['Accept-Encoding', 'Accept-Language'])
new Vary({ headerNames: ['Accept-Encoding', 'Accept-Language'] })

​
Raw Headers

Parse and stringify raw HTTP header strings. 
import { parse, stringify } from 'remix/headers'

let headers = parse('Content-Type: text/html\r\nCache-Control: no-cache')
headers.get('content-type') // 'text/html'
headers.get('cache-control') // 'no-cache'

stringify(headers)
// 'Content-Type: text/html\r\nCache-Control: no-cache'

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