'g' is invalid after a single JSON value. Expected end of data. LineNumber: L | BytePositionInLine: C.
This message comes from System.Text.Json JsonDocument on .NET 8.0.30. In this registry it is produced by 1 distinct mistake. Positions in the real message vary with your input; the causes do not.
Causes
What produces this message
Trailing characters after a JSON document
Input
{"a": 1} garbageExact message: 'g' is invalid after a single JSON value. Expected end of data. LineNumber: 0 | BytePositionInLine: 9.
Fix: Trim everything after the final closing brace, and check whatever produced the file for stray writes to stdout.
Same bug, other languages
What other parsers say about the same input
If a colleague reports a different message for what looks like the same file, this is why.
| Parser | Message for the same inputs |
|---|---|
| CPython json.loads | Extra data: line L column C (char N) |
| Gson | Use JsonReader.setLenient(true) to accept malformed JSON at line L column C path $… |
| Gson JsonParser (lenient off) | Use JsonReader.setLenient(true) to accept malformed JSON at line L column C path $… |
| JSON5 | JSON5: invalid character 'g' at 1:10 |
| JSON::PP | garbage after JSON object, at character offset N (before "…") |
| JavaScriptCore JSON.parse | JSON Parse error: Unable to parse JSON string |
| Newtonsoft.Json JsonConvert | Additional text encountered after finished reading JSON content: g. Path '', line L, position N. |
| Newtonsoft.Json JsonTextReader | Additional text encountered after finished reading JSON content: g. Path '', line L, position N. |
| Ruby JSON.parse | unexpected token at '…' |
| SpiderMonkey JSON.parse | JSON.parse: unexpected non-whitespace character after JSON data at line L column C of the JSON data |
| System.Text.Json Deserialize | 'g' is invalid after a single JSON value. Expected end of data. Path: $ | LineNumber: L | BytePositionInLine: C. |
| V8 JSON.parse | Unexpected non-whitespace character after JSON at position N (line L column C) |
| encoding/json Unmarshal | invalid character 'g' after top-level value |
| hjson | Syntax error, found trailing characters at line L,9 |
| json-bigint | Syntax error |
| json_decode | Syntax error |
| orjson | unexpected content after document: line L column C (char N) |
| serde_json::from_str | trailing characters at line L column C |
| ujson | Trailing data |
Sources
Standards this registry is checked against
- RFC 8259 (STD 90) — The JavaScript Object Notation (JSON) Data Interchange Format, T. Bray, Ed., 2017. The IETF Internet Standard for JSON. Obsoletes RFC 7159 and RFC 4627.
- ECMA-404, 2nd edition — The JSON Data Interchange Syntax, Ecma International, 2017. Ecma’s grammar for JSON. A normative reference of RFC 8259; the two define the same syntax.
- The Unicode Standard — The Unicode Standard, Core Specification, The Unicode Consortium, current. Normatively referenced by RFC 8259 for the definition of a character.
- IEEE 754-2019 — IEEE Standard for Floating-Point Arithmetic, IEEE, 2019. Referenced by RFC 8259 §6 as the basis for its interoperability guidance on numbers.
Only standards bodies and peer-reviewed venues are cited. Error strings on this site are observed by executing each parser; the standards above define what the parser is reacting to.