Unexpected end of JSON input

The document ended while the parser was still waiting for something — a closing brace, a closing quote, or in fact any content at all. Unlike most parse errors this one carries no useful position, because the problem is the absence of characters rather than a wrong one.

How the message appears

The same fault, worded by different engines. V8 (Chrome, Node, Edge) changed its format around Chrome 109, so older and newer runtimes disagree about the same document.

SyntaxError: Unexpected end of JSON input
SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data
SyntaxError: JSON Parse error: Unexpected EOF

What causes it

The string is empty

JSON.parse("") throws this exact error. An empty string is not valid JSON — null is. This is by far the most common source, usually from a response with no body.

The response had no body to parse

A 204 No Content reply, or a fetch whose body was already consumed. A Response body is a stream and can only be read once, so calling res.text() for logging and then res.json() leaves the second call nothing to read.

Truncated output

A file cut short by a full disk, a killed process, a stream written without being flushed or closed, or a log line clipped at a length limit. Open the end of the file: if the final brace is missing, the writer never finished.

An unclosed bracket, brace or string

Structurally the same thing — the parser is still inside a value when input runs out. An unterminated string is the sneakiest, because everything after the opening quote is swallowed as string content.

The fix

Close every structure that was opened. Here both the inner object and the outer object are missing their closing brace.

Fails to parse

{
  "user": {
    "name": "Ada",
    "id": 7

Parses

{
  "user": {
    "name": "Ada",
    "id": 7
  }
}

The example travels in the URL fragment, which browsers never send to a server.

Worth knowing

Guard the empty case rather than catching the throw: const data = text ? JSON.parse(text) : null.
Check response.ok and the content-type header before parsing. A failed request often returns HTML or nothing at all, and neither is JSON.