How do I find and remove trailing commas in a JSON file?

To find trailing commas, paste the JSON into a validator — it shows the exact line and column. To remove them, look for a comma followed only by whitespace before a closing brace } or bracket ]. In a text editor, the regex ,\s*([}\]]) can find trailing commas, and replacing it with $1 removes them. This regex is safe for JSON because commas inside string values are always followed by a value, not a closing brace. For automated fixing in code, the jsonrepair npm package removes trailing commas reliably. The safest long-term fix is to generate JSON with JSON.stringify, which never produces trailing commas.

How do I fix trailing comma errors in a JSON file automatically?

The jsonrepair npm package fixes trailing commas automatically. Install it with npm install jsonrepair and use: import { jsonrepair } from "jsonrepair"; const fixed = jsonrepair(brokenJson). It handles trailing commas in objects and arrays at any nesting level. For VS Code, installing the Prettier extension and setting the formatter to Prettier for JSON files will remove trailing commas when you save. For CI pipelines, running jsonrepair as a pre-processing step before parsing ensures downstream code never sees trailing commas. For new code, always use JSON.stringify to generate JSON — it never adds trailing commas.

Does jq remove trailing commas from JSON?

jq cannot parse JSON with trailing commas because it uses a strict JSON parser that follows RFC 8259. If you pipe a file with trailing commas to jq, it will error with "parse error". To work around this, pre-process the file to remove trailing commas before piping to jq. You can use sed: sed 's/,\s*}/}/g; s/,\s*\]/\]/g' input.json | jq . — though this regex is not safe for all cases. A more reliable approach is: python3 -c "import json,sys; print(json.dumps(json.load(sys.stdin)))" but Python also rejects trailing commas. Use jsonrepair or a JSONC-aware tool first, then pipe the cleaned output to jq.

Can I configure VS Code to prevent trailing commas in JSON?

Yes. Install the Prettier extension in VS Code and set it as the default formatter for JSON. Add to your settings.json or .vscode/settings.json: { "editor.defaultFormatter": "esbenp.prettier-vscode", "[json]": { "editor.formatOnSave": true } }. Prettier removes trailing commas when formatting JSON. For ESLint, the jsonc-eslint-parser plugin can lint JSON and JSONC files; enable the jsonc/no-trailing-commas rule to flag trailing commas. In a TypeScript or JavaScript project, the TypeScript compiler option "trailingComma" in your Prettier config controls trailing commas in JS/TS files, but for JSON files Prettier always removes them.

JSON Trailing Comma Error: How to Find and Fix It

Q: What is JSON5 and does it allow trailing commas?

JSON5 is a superset of JSON designed to be more human-friendly. It explicitly allows trailing commas in both objects and arrays. A JSON5 file like { name: "Alice", roles: ["admin",], } is valid JSON5 but invalid JSON. JSON5 also supports single quotes, unquoted keys, comments, and multi-line strings. It is used in some build tool configurations and config files. To parse JSON5, use the json5 npm package: import JSON5 from "json5"; const data = JSON5.parse(raw). However, JSON5 is not a suitable replacement for JSON in API communication — most HTTP clients and servers expect strict JSON.

Last updated: May 11, 2026

A trailing comma after the last value in a JSON object or array — {"a":1,} or [1,2,] — causes an immediate SyntaxError in every JSON parser, because RFC 8259 explicitly forbids trailing commas. The error message points to the closing bracket (} or ]), not the comma itself — V8 says {"SyntaxError: Unexpected token } in JSON at position N"}, Python says JSONDecodeError: Expecting value. JSON5 and JSONC (VS Code config files) both allow trailing commas, so the error only appears when the file is consumed by a standard JSON parser. This guide covers finding trailing commas by error position, automated fixers (json-repair npm package, jq, sed one-liners), and linting rules to prevent them.

What the error looks like

Different runtimes report the same problem differently:

// Node.js / V8
SyntaxError: Unexpected token '}' in JSON at position 42

// Firefox
SyntaxError: JSON.parse: unexpected character at line 4 column 1

// Safari
SyntaxError: JSON Parse error: Unexpected comma at end of array expression

// Python json module
json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes

All of them point to the character after the trailing comma, not the comma itself. The actual fix is one character before that position.

Trailing comma in an object

// ❌ Invalid — trailing comma after last property
{
  "name": "Alice",
  "role": "admin",
}

// ✅ Valid
{
  "name": "Alice",
  "role": "admin"
}

Trailing comma in an array

// ❌ Invalid — trailing comma after last element
["read", "write", "delete",]

// ✅ Valid
["read", "write", "delete"]

Nested trailing commas

Trailing commas can appear at any nesting level. The parser stops at the first one it finds.

// ❌ Invalid — trailing comma deep in a nested object
{
  "user": {
    "name": "Alice",
    "permissions": ["read", "write",]
  },
}

// ✅ Valid
{
  "user": {
    "name": "Alice",
    "permissions": ["read", "write"]
  }
}

Why JSON forbids trailing commas

The JSON specification (RFC 8259) was intentionally minimal. Trailing commas were excluded to keep parsers simple and to avoid ambiguity about whether a trailing comma implies a missing value. JavaScript object literals added trailing comma support later as a developer convenience, which is why the two formats look similar but behave differently.

If you need a JSON-like format that supports trailing commas and comments, consider JSONC (used by VS Code settings) or JSON5. For strict data interchange, use JSON.

How trailing commas get introduced

Hand-editing a JSON file and removing the last entry without removing its comma
Copy-pasting a JavaScript object literal into a JSON context
Building JSON by string concatenation instead of JSON.stringify()
A template or code generator that adds commas after every item

Prevent trailing commas in generated JSON

Always use JSON.stringify() to produce JSON programmatically. It never introduces trailing commas.

// Safe: JSON.stringify handles commas correctly
const payload = JSON.stringify({ name: "Alice", role: "admin" })
// → '{"name":"Alice","role":"admin"}'

// Unsafe: manual concatenation is error-prone
const unsafe = '{"name":"' + name + '","role":"' + role + '",}'

For more on safe JSON generation, see the JSON.stringify tutorial.

Fix pasted JSON with a validator

When the JSON comes from an external source — an API response, a config file, or a colleague's payload — paste it into a validator first. It will highlight the exact comma position so you can fix it in seconds rather than scanning the file manually.

Find the trailing comma instantly

Paste your JSON into Jsonic's JSON Validator. It shows the exact line and column of every syntax error, including trailing commas.

Open JSON Validator

Frequently asked questions

Why does JSON not allow trailing commas?

RFC 8259 excluded trailing commas for simplicity and to avoid ambiguity. JavaScript object literals added them later as a convenience, creating the confusion between the two superficially similar formats.

How do I find and remove trailing commas in JSON?

Paste into a validator for the exact line. To fix, find commas followed only by whitespace before a closing } or ]. The jsonrepair npm package removes them automatically.

What is JSON5 and does it allow trailing commas?

JSON5 is a superset of JSON that explicitly allows trailing commas, single quotes, unquoted keys, and comments. Parse it with the json5 npm package. It is not suitable for API data interchange.

How do I fix trailing commas automatically?

Use jsonrepair: import {'{ jsonrepair }'} from 'jsonrepair'. In VS Code, Prettier with format-on-save removes trailing commas from JSON files automatically.

Does jq remove trailing commas?

No — jq uses a strict JSON parser and errors on trailing commas. Pre-process the file withjsonrepair before piping to jq.

Can VS Code prevent trailing commas in JSON?

Yes. Install Prettier and enable editor.formatOnSave for JSON files. Prettier removes trailing commas when formatting. The jsonc-eslint-parser plugin can also lint for trailing commas.