JavaScript object literal passed off as JSON
Unquoted keys, single-quoted strings and trailing commas together — valid JavaScript source, not a JSON document.
The input
{a: 1, b: 'two', c: [3,],}{"a": 1, "b": "two", "c": [3]}How to fix it
Run it through `JSON.stringify()` from JavaScript, or convert by hand: quote the keys, switch to double quotes, drop the trailing commas.
JSON is a subset of JavaScript's literal syntax, not the other way round. Every JSON document is a valid JS expression; most JS object literals are not valid JSON.
What each parser reports
Every message below was captured by running this exact input through the parser named. 17 of 21 parsers rejected it; 4 accepted it.
| Parser | Exact message |
|---|---|
| CPython json.loads CPython 3.12.3 | Expecting property name enclosed in double quotes: line 1 column 2 (char 1)what this message means → |
| encoding/json Unmarshal Go go1.22.2 | invalid character 'a' looking for beginning of object key stringwhat this message means → |
| Gson Java 21.0.12 | Expected name at line 1 column 27 path $.cwhat this message means → |
| Gson JsonParser (lenient off) Java 21.0.12 | Expected name at line 1 column 27 path $.cwhat this message means → |
| hjson Node.js 22.22.2 | accepted — no error |
| Jackson ObjectMapper Java 21.0.12 | Unexpected character ('a' (code 97)): was expecting double-quote to start field namewhat this message means → |
| JavaScriptCore JSON.parse JavaScriptCore (Bun 1.4.1) | JSON Parse error: Expected '}'what this message means → |
| json-bigint Node.js 22.22.2 | Bad string |
| JSON5 Node.js 22.22.2 | accepted — no error |
| JSON::PP Perl 5.038002 | unexpected end of string while parsing JSON string, at character offset 2 (before ": 1, b: 'two', c: [3...")what this message means → |
| json_decode PHP 8.3.6 | Syntax error |
| Newtonsoft.Json JsonConvert Newtonsoft.Json 13.0.3 on .NET 8.0.30 | accepted — no error |
| Newtonsoft.Json JsonTextReader Newtonsoft.Json 13.0.3 on .NET 8.0.30 | accepted — no error |
| orjson CPython 3.12.3 | unexpected character, expected a string key: line 1 column 2 (char 1)what this message means → |
| Ruby JSON.parse Ruby 3.2.3 | unexpected token at '{a: 1, b: 'two', c: [3,],}' |
| serde_json::from_str Rust (serde_json 1.x) | key must be a string at line 1 column 2what this message means → |
| SpiderMonkey JSON.parse SpiderMonkey 115 | JSON.parse: expected property name or '}' at line 1 column 2 of the JSON datawhat this message means → |
| System.Text.Json Deserialize .NET 8.0.30 | 'a' is an invalid start of a property name. Expected a '"'. Path: $ | LineNumber: 0 | BytePositionInLine: 1.what this message means → |
| System.Text.Json JsonDocument .NET 8.0.30 | 'a' is an invalid start of a property name. Expected a '"'. LineNumber: 0 | BytePositionInLine: 1.what this message means → |
| ujson CPython 3.12.3 | Expected object or value |
| V8 JSON.parse Node.js 22.22.2 | Expected property name or '}' in JSON at position 1 (line 1 column 2)what this message means → |
What the specification says
The exact sections that govern this error. Descriptions are our paraphrase; follow the links for the normative text.
| Body | Section |
|---|---|
| IETF | A JSON text is a single value with optional surrounding whitespace ( JSON-text = ws value ws). The token set is six structural characters, strings, numbers and three literal names — nothing else. |
| IETF | Notes that JSON is a subset of JavaScript and that using eval() to parse it is an unacceptable security risk. |
| Ecma International | Lists the six structural tokens, the three literal name tokens, and the four whitespace code points. Whitespace is not allowed within a token. |
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