Convert NDJSON to Postgres
Upload a .json or .ndjson file and get back a Postgres SQL script you can load straight into your database. Types are preserved rather than flattened to text. Free, no registration, up to 10MB.
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CSV, Excel, SQLite, SQL, DBF (max 10 MB)
How your data is typed in Postgres
Generated from the converter's own Postgres type mapping — this is what it actually emits, not an example.
| Your data | Postgres type |
|---|---|
| Whole number | BIGINT |
| Decimal (money) | NUMERIC(10,2) |
| Floating point | DOUBLE PRECISION |
| True / false | BOOLEAN |
| Date | DATE |
| Date and time | TIMESTAMP |
| Short text | TEXT |
| Long text | TEXT |
| Binary data | BYTEA |
Working from an .ndjson file
Newline-delimited JSON is one complete object per line with no enclosing array, which is exactly what makes it appendable: a log or an export can keep growing without anything having to rewrite the end of the file.
- →Each line is parsed on its own and blank lines are ignored, but a single malformed or truncated line fails the whole file - the usual outcome of copying a log that was still being written.
- →Lines need not share their keys. The columns are what the records collectively use, and a record that omits one gets NULL in that column.
- →A file that is one line long and wraps its array, {"rows": [...]}, is unwrapped into those rows rather than read as a single record.
The oldest PostgreSQL this loads into
Postgres is the informal spelling and the one most people type. Since the name says nothing about a version, the useful question for this page is which server releases the generated script runs on, and that is decided by the newest piece of syntax in it.
- →The identity clause on auto-increment columns is the newest thing in the file, and it arrived in release 10. That is the floor for loading the script unedited.
- →Everything else is far older: the hex escape the script uses for binary values has been accepted since 9.0, and jsonb, which is what a JSON column is declared as, since 9.4.
- →On a server below the floor the script still loads if you delete the identity clauses by hand. The columns keep every value they were given, because each INSERT names them explicitly; they simply stop assigning new ones.
Reading NDJSON
- →JSON types are trusted: 1 and "1" stay different things.
- →Numbers with a decimal point are read as exact decimals rather than floats.
- →Both an array of objects and newline-delimited JSON work, and a wrapped array like {"data": [...]} is unwrapped automatically.
- →Nested objects are kept as JSON rather than flattened into invented column names.
Writing Postgres
- →Backslashes are left alone, because PostgreSQL treats them as ordinary characters — doubling them would corrupt every Windows path.
- →Auto-increment columns become GENERATED BY DEFAULT AS IDENTITY.
- →Binary data is written as bytea, and identifiers respect the 63-character limit.
What you get
A ZIP containing dump.sql, plus a README with the exact command to load it. If anything about your data needed a judgement call, a _warnings.txt explains it.
Load this dump into PostgreSQL: psql -U USER -d DATABASE -f dump.sql Create the database first if it does not exist: createdb -U USER DATABASE
Questions
- Is converting NDJSON to Postgres free?
- Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.
- Will my NDJSON data keep its types in Postgres?
- Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real Postgres types rather than everything becoming text. The mapping table above shows exactly what you get.
- Do you store my file?
- No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.