Fix malformed JSON Lines records

Step-by-step approach

Confirm there is one complete JSON value per physical line.
Validate each line independently; JSONL is not one giant JSON array.
Use the JSONL validator to identify invalid line numbers.
Review dropped lines before exporting only valid records to prevent accidental data loss.
Re-run validation on the exported file.

Try the matching tool

Open JSONL Validator to work on a local copy. Review the result before importing it elsewhere.

What this does not solve

Browser tools can validate known structures and transform available data, but cannot restore deleted or corrupted bytes, infer unknown business facts, or guarantee that a target system will import every field as intended.