$ toolfu run jsonl-validator
JSONL Validator — Validate JSON Lines Online Free
Free online JSONL validator. Validate JSON Lines data line by line, highlight broken rows, and convert JSONL to JSON array — runs in your browser.
all processing runs in your browser
jsonl-validator
input > paste JSONL
3 valid1 invalid4 total lines
errors
line 3Expected ',' or '}' after property value in JSON at position 18 (line 1 column 19)
line results
1✓{"name":"Alice","age":30}
2✓{"name":"Bob","age":25}
3✗{"name":"Charlie" age:40}
4✓{"name":"Diana","age":35}
json array output
[
{
"name": "Alice",
"age": 30
},
{
"name": "Bob",
"age": 25
},
{
"name": "Diana",
"age": 35
}
]
Validate JSONL Files Instantly
JSONL (JSON Lines) is a popular format for streaming data, log files, and ML datasets. Each line should be a valid JSON value. When a single malformed line breaks your data pipeline, you need to find it fast.
This tool validates each line of your JSONL data independently, highlights broken rows with line numbers and error messages, and gives you a count of valid vs. invalid lines. It also converts the valid lines into a standard JSON array you can copy.
When to use this validator
- Debugging broken JSONL exports from APIs or databases
- Validating ML training data before feeding it to a model
- Converting JSONL to a JSON array for tools that need it
- Checking log file formats line by line
$ cat FAQ.md
What is JSONL?▶
JSONL (JSON Lines) is a text format where each line is a valid JSON value, typically a JSON object. It's commonly used for streaming data, log files, and machine learning datasets because each line can be parsed independently without loading the entire file into memory.
How is JSONL different from a JSON array?▶
A JSON array wraps all items in square brackets with commas between them, requiring the entire file to be parsed at once. JSONL puts one JSON object per line with no separating commas or wrapping brackets, making it streamable and appendable.
Is my data sent to a server?▶
No. This validator runs entirely in your browser. Your data never leaves your device — each line is parsed locally using JSON.parse.
Can I convert JSONL to a JSON array?▶
Yes. This tool automatically generates a JSON array from all valid lines. Click the copy button on the JSON array output to get the converted result.