About jsonl.co
jsonl.co is a free collection of online tools for viewing, editing, validating, and converting JSONL (JSON Lines / NDJSON) files. Everything runs entirely in your browser — your files are never uploaded to a server.
Our mission
Make working with JSONL effortless. Whether you're inspecting an OpenAI fine-tuning dataset, debugging a multi-gigabyte log file, or converting JSON Lines to CSV, jsonl.co aims to give you fast, reliable, privacy-first tools that just work — with no sign-up and no upload.
Why I built this
Most existing JSONL tools either upload your file to a server or freeze on anything larger than a few megabytes. As a developer who works with large datasets and AI training data, I wanted something that opens 1GB+ files instantly, keeps data on my own machine, and is genuinely free. jsonl.co is the tool I wished existed.
Privacy by design
Every tool on jsonl.co runs 100% client-side using JavaScript in your browser. Your JSONL files are processed locally and never leave your device — there are no uploads, no accounts, and no tracking of your file contents. You can read the full details in our Privacy Policy.
Who's behind jsonl.co
jsonl.co is built and maintained by Jerry, an independent developer. It's an ongoing solo project, and feedback from the people who use it shapes what gets built next. If you have a suggestion, a bug report, or just want to say hello, I'd love to hear from you.
Have a question, found a bug, or want to request a feature? Get in touch.