JSONL Key Case Converter
Normalise every key in a JSONL file to one convention. snake_case for a warehouse, camelCase for a JavaScript client, PascalCase for .NET — applied recursively through nested objects and arrays, with a warning when two keys would collapse into one.
Convert
Where the word boundaries fall
userName→user_name— a lowercase-to-uppercase transition starts a new word.user_name→userName— separators are consumed.HTTPServer→httpserver, nothttp_server. A run of capitals counts as one word, so acronyms need checking by hand.user2Name→user2_name— digits stay with the word before them.
Use lowercase or UPPERCASE when you want a straight case change with no word splitting at all — useful for keys that are already single words.
Collisions are silent data loss
If a file contains both userName and user_name — which happens whenever two
producers write to the same stream — converting to snake_case maps them onto one key and one value wins.
There is no way to preserve both, so the status bar turns amber and counts the collisions.
Find the offenders first with Field coverage: two near-identical field names with complementary coverage percentages is the signature. Then decide deliberately which one to keep, using Find & replace, before normalising the rest.
Privacy
Nothing is uploaded. The whole thing runs in this tab, in your own browser. That matters here more than on most tool sites — training data is usually the most sensitive file a team owns.
Frequently asked questions
Does it change values?
No. Only keys are renamed; values pass through untouched.
Is key order preserved?
Yes, keys keep their original order. Use Sorter if you want them sorted.
Are keys inside arrays converted?
Yes — arrays are traversed and every object inside them is processed at any depth, unless you tick Top-level keys only.
Which case should I pick for a warehouse?
snake_case. BigQuery, Snowflake, Redshift and Postgres all fold unquoted identifiers, and snake_case avoids ever needing to quote them.