Description
Plan comma combination only for explicit caller-qualified list fields, always preserving Set-Cookie as uncombined; no universal field-combination inference.
HTTP field names are case-insensitive, while values follow each field’s own grammar. Repeated occurrences sometimes form lists but cannot always be combined. Quoted values, optional spaces/tabs and quality weights need their own treatment; the tools here use explicit field records or a stated text subset.1
Plan comma combination only for explicit caller-qualified list fields, always preserving Set-Cookie as uncombined; no universal field-combination inference.
When to use this tool
Use this tool to plan comma combination only for explicit caller-qualified list fields, always preserving Set-Cookie as uncombined; no universal field-combination inference.
How to use the tool and how it works
- Enter headersJson, combinableNames using the field definitions below. For JSON text, serialize the explicit records in the shown shape.
- Run the operation. Correct input errors before interpreting an output.
- Read result.plan. Use the ordering, boundary rules and absence conditions described below.
Group headers case-insensitively. For caller-approved combinable names except Set-Cookie, join values with comma-space; otherwise return combined null.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| headersJson | JSON text encoding array of {name: string, value: string}. Keep the record keys and value types shown in the decoded example below. | Text, at most 8,192 UTF-16 code units; the operation’s grammar also applies. |
| combinableNames | Caller-declared list-valued names eligible for comma combination; Set-Cookie is always excluded. | Dense list of at most 128 strings, each at most 8,192 UTF-16 code units. |
These are the decoded structures used in the example’s JSON text fields. Supply the corresponding serialized JSON strings as input.
{
"headersJson": [
{
"name": "X-A",
"value": "one"
},
{
"name": "x-a",
"value": "two"
},
{
"name": "Set-Cookie",
"value": "a=1"
}
]
}| Output field | Interpretation |
|---|---|
| result | Object containing the named fields below. |
| result.plan | Per-name combination plan; combined is null when combination is not allowed. |
{
"input": {
"headersJson": "[{\"name\":\"X-A\",\"value\":\"one\"},{\"name\":\"x-a\",\"value\":\"two\"},{\"name\":\"Set-Cookie\",\"value\":\"a=1\"}]",
"combinableNames": [
"x-a",
"set-cookie"
]
},
"output": {
"result": {
"plan": [
{
"name": "x-a",
"indexes": [
0,
1
],
"combined": "one, two"
},
{
"name": "set-cookie",
"indexes": [
2
],
"combined": null
}
]
}
}
}Limitations and assumptions
- The caller must supply the field-specific combination policy; Set-Cookie is always left uncombined.
- Explicit header records have name and value strings. Names must use token syntax; supported value code units are tab or 32–255 excluding DEL. Byte budgets use that single-byte representation, not UTF-8 or HTTP/2 compression.
- Every declared top-level input field is required and unexpected fields are rejected. Ordinary strings are limited to 8,192 UTF-16 code units and lists to 128 entries, with tighter operation-specific bounds where stated. JSON text has bounded nesting and node counts.
- Numeric outputs must be finite and no larger in absolute magnitude than the safe-integer limit; operations returning exact large integers use decimal text. Positions are zero-based and spans end exclusively unless the operation explicitly states a different convention.
Alternative or Complementary methods
Choose field-specific parsing and combination rules rather than applying one policy to every header. Preserve occurrence order and use a full HTTP implementation for message framing and protocol-level decisions.
References
-
RFC 9110: HTTP Semantics — RFC Editor
-
Tool behavior and example: HTTP Header List Combination Plan — tool.io
Similar or alternative tools
- HTTP Header Top-Level Comma Token Splitter
Split HTTP comma lists with the existing quote/escape-aware scanner, not generic parentheses or CSS syntax; trims outer whitespace and preserves quoted text.
- HTTP Header Line First Colon Splitter
Split one HTTP field line at its first colon, validating a nonempty token name while retaining raw value whitespace; CR/LF or obs-fold are rejected.