JSONL Minifier

updated 12 May 2026

JSONL minifier. Compress a JSONL (JSON Lines) file: strip whitespace, optionally drop null and empty fields, optionally remove unwanted keys. Up to 1 GB, runs in your browser.

What "minify" means here

By default, minification strips whitespace inside each record so every line becomes the tightest possible JSON. Toggle Drop null fields to remove keys whose value is null, and Drop empty to remove empty strings, arrays, and objects. You can also list keys to remove explicitly — handy for stripping fields like debug or internal_id before sharing a file.

Before you start

You need a .jsonl or .ndjson file (one JSON object per line). The minifier won't touch records it can't parse — broken lines are passed through as-is so you can fix them with the Auto-fixer first.

How to use it

1. Drop a file or paste JSONL into the Input pane.
2. Optional: tick Drop null fields to remove keys whose value is null.
3. Optional: tick Drop empty to remove empty strings, arrays and objects.
4. Optional: list keys you want gone in the Remove keys box (one per line, dot.notation supported for nested keys).
5. Click Minify. The status bar shows bytes-in vs bytes-out and the percent saved.
6. Click Download or Copy.

Options explained

Drop null fields

Removes any key whose value is exactly null. Useful before loading into a typed system (BigQuery, Parquet, Postgres) where null columns count toward your width.

Drop empty

Removes "", [] and {}. Aggressive but very effective for compressing sparse event logs.

Remove keys

Explicit key paths to delete, one per line. created_at drops the top-level key, meta.debug drops a nested key. Works across all records.

Example

Input (each line pretty-printed for clarity):

{ "id": 1, "user": "alice", "meta": { "debug": true, "ip": null } }
{ "id": 2, "user": "bob",   "meta": { "debug": false, "ip": "10.0.0.1" } }

With Drop null on and meta.debug in the remove list:

{"id":1,"user":"alice","meta":{}}
{"id":2,"user":"bob","meta":{"ip":"10.0.0.1"}}

Tips & common pitfalls

• Order matters in the pipeline. Validate first (Validator) → fix (Auto-fixer) → then minify. Otherwise broken lines silently pass through.
• Drop empty is destructive. An empty array tags: [] is information ("this record has no tags") in some schemas. Don't toggle it if downstream code distinguishes empty from missing.
• Use the JSON-Schema validator (link) after minifying to confirm you didn't strip a required field by accident.
• Big wins on logs. Server-log JSONL with many optional fields often shrinks 30–60% with Drop null + Drop empty.

Frequently asked questions

Related tools

• JSONL FormatterPretty-print the same file with a configurable indent.
• JSONL ValidatorLine-by-line syntax check before minifying.
• JSONL AnonymizerRemove or mask PII fields with built-in detectors.
• Auto-fixerRepair broken JSONL before minifying.