Guides / JSON errors
“Expected double-quoted property name in JSON”
How it appears per engine
- Uncaught SyntaxError: Expected double-quoted property name in JSON at position 8 (Chrome / Node.js)
- SyntaxError: JSON.parse: expected double-quoted property name at line 1 column 9 of the JSON data (Firefox)
What this error means
After a comma inside an object, the parser expects the next property name in double quotes. The classic trigger is a trailing comma before the closing brace — the comma promises another property that never arrives.
Common causes
1. A trailing comma before }
Trailing commas are fine in modern JavaScript and in JSON5 config files, but the JSON standard (RFC 8259) forbids them.
Fails
{
"a": 1,
"b": 2,
}Works
{
"a": 1,
"b": 2
}2. Keys quoted with the wrong characters
Single quotes, backticks, or “smart quotes” pasted from a chat app or word processor all fail. Only straight double quotes (") are JSON.
Fails
{ “a”: 1 }Works
{ "a": 1 }3. A comment where a key should be
JSON has no comments. Tools like tsconfig.json accept them (that is JSONC), which trains people to expect they work everywhere.
How to fix it
- Delete the comma after the last property in every object and array.
- Replace curly/smart quotes with straight double quotes — re-type them if you pasted from a document.
- Strip // and /* */ comments.