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Technical Vocabularynoun · /ˈhedər/

header

header — In tech, a header is metadata or information placed at the beginning of a request, response, file, or document that provides instructions or context.

In simple English

Headers appear in multiple tech contexts. In web development, HTTP headers are part of requests and responses that carry information like content type, authentication tokens, and caching rules. In data processing, file headers contain metadata about the file format or structure. In documents and emails, headers are the top sections containing titles or sender information. In tables or spreadsheets, headers are the first row identifying column names. Understanding headers is critical because they control how systems interpret and handle data, making them fundamental to nearly every tech workflow from APIs to databases.

What is a header in programming, web development, or HTTP requests?

At a glanceCEFR B2
Commonness5/5
Versatility5/5
FormalityCasualFormalNeutral
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticDirect
RegionUS and UK

Say it like this

  • Set the headers before sending the request
  • Check the response headers for errors
  • Add the authorization header to your request

Use it at work

APIs

  • Send the token in the Authorization header.
  • The response header says the cache expired.

Debugging

  • The request is missing the Content-Type header.
  • Check the headers in the network tab.

Design

  • The page header is too tall on mobile.
  • Add the logo to the header.

Don't say this

✕The header is sending in the body of the request.
✓The header is included in the request, not in the body.

Headers are separate from the body; they provide metadata about the request itself, not data within it.

Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. Your colleague asks how to send authentication information with an API call. What do you say?

Complete the sentence

2. Always check the _______ to see what format the server is expecting for the response.

Spot the mistake

3. Which sentence uses header incorrectly?

Rewrite naturally

4. Rewrite this sentence more naturally using header: 'The information at the top of the request tells the system how to read the rest of the information.'

Say it out loud

Phrase 1 of 3

"Set the headers before sending the request"

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More about header

Real examples(3)

  • in a code review

    "Did you remember to include the Content-Type header in your POST request?"

  • in a standup

    "I spent two hours debugging why the API call failed, then realized I forgot to add the authentication header."

  • in a team meeting

    "We need to document which headers are required and which ones are optional for the new endpoint."

More mistakes(2)

Handle with care. Avoid confusing HTTP headers with document headers or heading styles. Context determines which meaning applies.

  • ✕We forgot to header the request with authentication.
    ✓We forgot to include the authentication header in the request.

    Header is a noun, not a verb in this context. Use include, add, or set with headers.

  • ✕The server returned an error in its header.
    ✓The server returned an error in the response headers.

    Headers are typically plural when referring to multiple key-value pairs, or use the singular for a specific header.

Other forms(3)

  • header noun

    "The API request requires an authorization header."

  • headers noun (plural)

    "Make sure all the headers are formatted correctly."

  • header field noun (compound)

    "The User-Agent header field identifies the client making the request."

Often used with(6)

  • set/add/include a header · These verbs are used to place headers in requests or responses
  • HTTP header · Most common phrase referring to headers in web communication
  • header value · The specific data or content assigned to a header key
  • custom header · Headers that are user-defined rather than standard protocol headers
  • response header · Headers returned by a server in response to a client request
  • request header · Headers sent by a client as part of its request to a server

Similar words(3)

  • metadata · Broader term; headers are a specific type of metadata
  • attribute · General term for properties; less specific than header in tech contexts
  • field · Used similarly in some contexts but less precise for HTTP communication

Opposites(2)

  • body (the main content after headers)
  • payload (the data being sent, distinct from headers)

Questions(5)

What does header mean in software engineering?
A header is metadata information placed at the beginning of a request, response, file, or document. In HTTP communication, headers are key-value pairs that provide instructions about how to process the data that follows. For example, a Content-Type header tells the system what format the data is in.
How do you use header in a sentence at work?
You use header as a noun in phrases like: Set the authorization header before sending the request, Check the response headers for error details, or Add a custom header to the API call. Use verbs like set, add, include, or check with headers.
Is header formal or informal?
Header is neutral in formality. It is equally appropriate in casual standup conversations (Did you add the header?) and formal documentation (The request must include the specified headers). It is a standard technical term used in all professional settings.
What are the most common headers in web development?
Common headers include Content-Type (specifies data format), Authorization (carries authentication tokens), Accept (tells the server what formats the client accepts), User-Agent (identifies the client), and Cache-Control (controls caching behavior). Each serves a specific purpose in HTTP communication.
Can header be used as a verb?
In technical English, header is primarily a noun. While some people informally say to header something, the correct usage is to set, add, or include a header. Using header as a verb is considered non-standard and should be avoided in professional settings.
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