jsonlkit.com
JSONL (JSON Lines) utilities, in the browser
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Changelog

What's new on jsonlkit.com · most recent first

A short, honest log of what's been added, changed, or fixed. No marketing — just the actual edits. If something here looks broken or missing, please drop a note to [email protected].

2026-05-07 · Home page redesign

  • Tool first. The auto-fixer is now embedded directly on the home page so you can paste a broken JSONL line and see it repaired without an extra click.
  • Full-width layout. Removed the fixed-width container so the tool panes can use the whole window.
  • Sidebar moved to footer. The left tool list is now a tile grid in the page footer, grouped by Convert / Inspect / Transform / Sample data.
  • Link colors. Links in body copy now read as links — bold links inherit the link color instead of falling back to ink.
  • Acronym annotations. Pages now spell out JSONL (JSON Lines) on first mention so first-time visitors aren't guessing.

2026-05-04 · JSONL Auto-Fixer

  • Conservative repair pipeline: trailing commas, single → double quotes, smart quotes, NaN / Infinity / undefined, BOMs, unquoted keys, JS comments, leading garbage.
  • Re-parses each fixed line — if it still doesn't pass JSON.parse, the line is reported with column and a suggested fix instead of being silently emitted.

2026-04-25 · Dataset stats panel

  • Drop a JSONL file and get row count, duplicate rate, parse errors, and a per-field table with fill rate, type histogram, distinct count, and top values.

2026-04-18 · LLM fine-tune validator covers three formats

  • OpenAI chat (messages), Anthropic (top-level system + alternating user/assistant), and the legacy OpenAI prompt/completion shape.
  • Picker dropdown so you validate against the format you're actually training on.

2026-04-10 · Token counter

  • Estimates total tokens per file and projects fine-tune cost per model so you can budget the run before submitting.

2026-03-22 · JSONL ↔ Parquet

  • Convert JSONL to Parquet (and back) entirely in the browser using DuckDB-WASM. Compressed columnar output ready to drop into a warehouse.

2026-03-05 · Schema inferrer

  • Walks every record and emits a Draft-07 JSON Schema with required fields, union types, and enum detection.

Earlier

Initial release: validator, viewer, formatter, deduplicator, splitter / merger, and converters for CSV ↔ JSONL and JSON ↔ JSONL. All 100% client-side.