Unity-Technologies/UnityCsReference · error · JSONParseException

Invalid unicode escape char near {}

Error message

Invalid unicode escape char near {}

What it means

Thrown by the Asset Store JSON parser when a \uXXXX unicode escape sequence inside a JSON string contains characters that are not valid hexadecimal digits. The parser extracts four characters after \u and calls Int32.Parse with AllowHexSpecifier; a FormatException from that call triggers this error. It indicates the JSON payload is malformed at the unicode escape position.

Source

Thrown at Editor/Mono/AssetStore/Json.cs:581

                        res += '\t';
                        break;
                    case 'u':
                        // Unicode char specified by 4 hex digits
                        string digit = "";
                        if (endidx + 4 >= len)
                            throw new JSONParseException("End of json while parsing while parsing unicode char near " + PosMsg());
                        digit += json[endidx + 1];
                        digit += json[endidx + 2];
                        digit += json[endidx + 3];
                        digit += json[endidx + 4];
                        try
                        {
                            int d = System.Int32.Parse(digit, System.Globalization.NumberStyles.AllowHexSpecifier);
                            res += (char)d;
                        }
                        catch (FormatException)
                        {
                            throw new JSONParseException("Invalid unicode escape char near " + PosMsg());
                        }
                        endidx += 4;
                        break;
                    default:
                        throw new JSONParseException("Invalid escape char '" + ncur + "' near " + PosMsg());
                }
                idx = endidx + 1;
            }
            if (idx >= len)
                throw new JSONParseException("End of json while parsing while parsing string near " + PosMsg());

            cur = json[idx];

            Next();
            return new JSONValue(res);
        }

        private JSONValue ParseNumber()

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Inspect the raw JSON payload at the reported position to find the malformed \u escape and correct the hex digits.
2. Clear the Asset Store cache (Library/PackageManager or Editor pref cache) and re-fetch the data to get a clean response.
3. If the data originates from a server endpoint, verify the server-side JSON serialization handles unicode correctly.
4. If you control the JSON producer, ensure all unicode codepoints are emitted as valid 4-digit hex \uXXXX sequences.

Example fix

// before — malformed payload
string json = "{\"name\": \"caf\\u00G9\"}";
// after — valid hex digits
string json = "{\"name\": \"caf\\u00e9\"}";

// Pre-validate \u escape sequences before parsing
bool HasValidUnicodeEscapes(string json)
{
    for (int i = 0; i < json.Length - 5; i++)
    {
        if (json[i] == '\\' && i + 1 < json.Length && json[i + 1] == 'u')
        {
            for (int j = 2; j <= 5; j++)
            {
                char c = json[i + j];
                if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')))
                    return false;
            }
        }
    }
    return true;
}

try
{
    var result = JSONParser.SimpleParse(jsonString);
}
catch (JSONParseException ex) when (ex.Message.Contains("unicode escape"))
{
    // Log the raw JSON region and re-fetch or sanitize
    Debug.LogError($"Malformed unicode escape in JSON: {ex.Message}");
}

When it happens

Trigger: Parsing a JSON string containing a \u escape followed by non-hex characters (e.g. "\u00GG" or "\u00"). Occurs when AssetStoreClient or AssetStoreTooling deserializes a response from the Unity Asset Store server that contains a corrupted or truncated unicode escape sequence.

Common situations: Truncated network responses from the Asset Store API, proxy or CDN corruption of JSON payloads, manually-edited or hand-crafted JSON cache files with invalid escapes, character encoding issues where multi-byte sequences are split.

Related errors

• Invalid escape char '{}' near {}
• End of json while parsing while parsing string near {}
• Cannot convert string to float : '{}' at {}
• Invalid token at {}
• End of json while parsing while parsing unicode char near {}

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/81bbac6a5db23643. Report an issue: GitHub.