title: Header Parameters
description: Read and validate HTTP header parameters in JustAPI.
keywords: [JustAPI, header parameters, HTTP headers, validation]

Basic Header Parameters

from justapi import JustAPIApp, Header

app = JustAPIApp()

@app.get("/items/")
def read_items(x_token: str = Header(...)):
    return {"x_token": x_token}

The header name X-Token is automatically converted to x_token (underscores).

Multiple Headers

@app.get("/users/")
def read_users(
    x_token: str = Header(...),
    x_request_id: str = Header(None),
):
    return {"x_token": x_token, "x_request_id": x_request_id}

Required vs Optional

• Header(...) — required (the ... means "no default, required")
• Header(None) — optional, defaults to None
• Header("default") — optional, defaults to "default"

Underscore Conversion

By default, JustAPI converts dashes to underscores in header names. To disable this:

@app.get("/items/")
def read_items(custom_header: str = Header(..., convert_underscores=False)):
    return {"custom_header": custom_header}

Duplicate Headers

For headers that can repeat (like Set-Cookie):

@app.get("/items/")
def read_items(x_token_list: list[str] = Header(...)):
    return {"x_token_list": x_token_list}

See Also

• Cookie Parameters — reading cookies
• Request Body — JSON request bodies