karatelabs/karate · error

Unterminated JSON string

Error message

Unterminated JSON string

What it means

Thrown by JsonParser.parseString when the closing double quote of a JSON string is never found — the input ends while still inside a string. Every JSON string must be terminated by '"', so a string that runs to end-of-input is malformed.

Solutions

1. Inspect the string being parsed and add the missing closing '"'.
2. Check for an unintended backslash before the closing quote ('\"' escapes it) and remove or double the backslash.
3. Verify the payload wasn't truncated in transit — read the full response/file.
4. Use a JSON serializer to produce strings so quoting is always balanced.

Example fix

// before
'{"name": "karate' // missing closing quote
// after
'{"name": "karate"}'

// Check quote balance (ignoring escapes) before parsing
static boolean hasUnterminatedString(String s) {
    boolean inStr = false;
    for (int i = 0; s != null && i < s.length(); i++) {
        char c = s.charAt(i);
        if (c == '\\') { i++; continue; }
        if (c == '"') inStr = !inStr;
    }
    return inStr;
}

try {
    return Json.parse(raw);
} catch (JsonSyntaxException e) {
    if (e.getMessage().equals("Unterminated JSON string")) {
        throw new IllegalArgumentException("Missing closing quote; raw=" + raw, e);
    }
    throw e;
}

When it happens

Trigger: Parsing input like '{"a": "value' — an opening quote with no matching closing quote before end of input, usually from truncation or a missing/escaped-away quote.

Common situations: Truncated HTTP bodies or file reads, an accidental '\"' that escaped the intended closing quote, template interpolation that dropped the quote, hand-edited JSON missing the final quote.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

• Expected ':' after object key
• Expected ',' or ']' in array
• Expected ',' or '}' in object
• Expected string key in object
• Invalid literal — expected 'false'

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/8dfed80314c3aa53. Report an issue: GitHub.

Appendix: source

Thrown at karate-js/src/main/java/io/karatelabs/js/JsonParser.java:234

                            break;
                        case 't':
                            sb.append('\t');
                            break;
                        case 'u':
                            sb.append(parseHex4());
                            break;
                        default:
                            throw syntaxError("Invalid escape '\\" + esc + "' in JSON string");
                    }
                    continue;
                }
                if (c < 0x20) {
                    throw syntaxError("Invalid control character in JSON string");
                }
                sb.append(c);
                pos++;
            }
            throw syntaxError("Unterminated JSON string");
        }

        private char parseHex4() {
            if (pos + 4 > len) {
                throw syntaxError("Invalid \\u escape in JSON string");
            }
            int v = 0;
            for (int i = 0; i < 4; i++) {
                char h = s.charAt(pos + i);
                int d;
                if (h >= '0' && h <= '9') d = h - '0';
                else if (h >= 'a' && h <= 'f') d = 10 + (h - 'a');
                else if (h >= 'A' && h <= 'F') d = 10 + (h - 'A');
                else throw syntaxError("Invalid hex digit '" + h + "' in \\u escape");
                v = (v << 4) | d;
            }
            pos += 4;
            return (char) v;

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