Missing Quotes
JSON keys must use double quotes. A JavaScript object can sometimes use unquoted keys, but valid JSON cannot. If a parser complains near a key name, check the quotes first.
Trailing Commas
A comma after the last item in an object or array is a common error. Some tools tolerate it, but strict JSON parsers reject it. Remove the final comma before a closing brace or bracket.
Wrong Brackets
Objects use curly braces and arrays use square brackets. If the structure is nested, one missing bracket can make the rest of the file look broken. Formatting the JSON with indentation makes bracket problems easier to see.
Invalid Values
JSON supports strings, numbers, booleans, null, arrays, and objects. Values such as undefined, comments, and single-quoted strings are not valid JSON.
Common Error Patterns
Most JSON mistakes are small but strict. A trailing comma after the last item, a missing quotation mark, or a single quote instead of a double quote can stop the whole file from parsing. Another frequent issue is copying JavaScript-style comments into JSON, even though plain JSON does not allow comments.
How to Debug Faster
When a JSON file fails, format it first so nesting becomes visible. Then check the line near the reported error and the line immediately before it. Parser messages often point to where the parser became confused, not where the mistake originally started. Validate small sections if a large payload is hard to read.
Safer JSON Habits
Keep sample payloads separate from production secrets. Remove API tokens, passwords, customer records, and private IDs before sharing JSON in support tickets or screenshots. For repeated work, save a known-good example and compare new payloads against it whenever an import or API request starts failing.