Calculator
What the HTTP Header Generator does
HTTP Header Generator: generates Status and HTTP headers from Header set. Example: header set CORS (permissive) gives status Headers ready.
The HTTP Header Generator takes Header set and returns Status and HTTP headers. You can nudge a single number and watch the effect straight away.
Most people who open the HTTP Header Generator are people inspecting an API response. Most of these tasks are one-liners in a terminal, but not when you are away from one.
There is no back end here. The calculation runs where you are sitting, not on a server somewhere.
Further down the page: what each field expects, how the result is derived, and one example worked from the defaults.
What do the HTTP Header Generator fields mean?
The HTTP Header Generator uses 1 input. Pre-filled inputs double as documentation: each one shows what a reasonable value looks like.
| Field | What to enter | Default |
|---|---|---|
| Header set | choose from CORS (permissive), Security headers, Cache static assets or JSON API response | CORS (permissive) |
How does the HTTP Header Generator work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same generated output.
Values are checked first: an out-of-range or non-numeric entry names the offending field instead of returning nonsense.
Worked example
These are the values the HTTP Header Generator loads by default, and the result it produces from them. This is the worked example the page starts from, reproduced here so you can check the arithmetic.
| Header set | CORS (permissive) |
|---|
| Status | Headers ready |
|---|---|
| HTTP headers | Access-Control-Allow-Origin: * Access-Control-Allow-Methods: GET, POST, OPTIONS Access-Control-Allow-Headers… |
How to use it
- Pick a value for Header set: the options are CORS (permissive), Security headers, Cache static assets or JSON API response.
- You will see the result move while you are still editing: that is expected.
- The results panel then shows Status and HTTP headers.
- Copy Link puts the current inputs in the URL, so bookmarking it brings the same numbers back.
What this tool does not do
- Output follows the common convention for this format; a specific toolchain may have its own house style.
- Processing happens in your browser, so extremely large inputs are bounded by available memory.
- It cannot detect a typo that happens to fall inside the valid range.
Frequently asked questions
You need Header set. Every box already holds a working value, which means a single edit is enough to get a meaningful answer.
With the values loaded when the page opens, status comes out as Headers ready. The figure is derived from the inputs above, so it updates whenever they do.
It never leaves the tab. The page does the work itself rather than asking a server to.
No. There is no account, no usage cap and no trial period. The site is funded by advertising rather than by charging for the tools.
The generated output is exact for the method described above. Where a value is rounded for display, the underlying figure keeps full precision.