CSS Font Family List Parser

Description

Parse a restricted CSS font-family list of JSON-double-quoted strings or valid unescaped ASCII identifier sequences; CSS escape and single-quoted syntax is intentionally rejected.

CSS combines token syntax, property-specific value rules and layout/cascade processing. These are separate layers: splitting a declaration does not establish that its value is valid, and arithmetic on resolved lengths does not perform browser layout. Each tool here handles an explicit numeric representation or a stated lexical subset.

Parse a restricted CSS font-family list of JSON-double-quoted strings or valid unescaped ASCII identifier sequences; CSS escape and single-quoted syntax is intentionally rejected.

When to use this tool

Use this tool to parse a restricted CSS font-family list of JSON-double-quoted strings or valid unescaped ASCII identifier sequences; CSS escape and single-quoted syntax is intentionally rejected.

How to use the tool and how it works

Enter text using the input definitions below.
Run the operation. Resolve malformed-input errors before interpreting the result.
Read result.families. Interpret signs, units, ordering and null values using the rules below.

Split at top-level commas while respecting balanced quotes/groups. Trim each item; parse double-quoted items as JSON strings, otherwise require an unescaped ASCII identifier sequence separated by single spaces.^{[1, 2]}

Input field	Meaning and units	Accepted input
text	CSS-subset text to parse under the operation’s stated grammar.	Text, at most 8,192 UTF-16 code units; the stated grammar and narrower limits also apply.

Output field	Interpretation
result	Object containing the fields below.
result.families	Parsed family-name strings in list order.

json

{
  "input": {
    "text": "\"A B\", serif"
  },
  "output": {
    "result": {
      "families": [
        "A B",
        "serif"
      ]
    }
  }
}

Limitations and assumptions

Single-quoted strings, CSS hexadecimal escapes and the full font-family grammar are unsupported. Generic keywords are returned as text without font resolution.
Lengths and times must already be resolved to consistent numeric units. Lexical helpers intentionally support smaller grammars than a full browser CSS parser; malformed supported-subset input causes an error.
Every declared top-level input is required and unknown 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 within the absolute safe-integer magnitude; exact larger integers use decimal text. Source positions are zero-based UTF-16 offsets and span ends are exclusive unless a different convention is explicitly stated.

Alternative or Complementary methods

Use a full CSS parser or browser style/layout APIs when escape handling, error recovery, computed styles or the full cascade matter. These tools expose focused transformations and audits of supplied data.

References

CSS Fonts: Font Family Names — W3C
Tool behavior and example: CSS Font Family List Parser — tool.io

Similar or alternative tools

CSS Font Family List Formatter
Format literal font family names as double-quoted escaped CSS strings using JSON-compatible escapes; control characters are rejected, generic keywords become literal family names.
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