YOLO's NDJSON
Converter
Convert Ultralytics NDJSON and JSONL exports to YOLO, COCO JSON, and Pascal VOC formats. Fast, private, and runs entirely on your machine.
curl -fsSL https://yolondjson.zip/install.sh | shAvailable on macOS, Windows, and Linux · ~5 MB
Having trouble? Check the troubleshooting guide
Why I Built This
A small companion tool for Ultralytics users
Built on Love for Ultralytics
Ultralytics Platform is genuinely one of the best tools for vision AI - fast, intuitive, and constantly pushing boundaries. I use it daily and love what they're building for the community.
Bridging the Gap
Their NDJSON export works great inside the Ultralytics ecosystem. But when I wanted to train locally, try other frameworks, or simply browse my dataset as organized folders - the manual conversion added up. So I built this tool to do it all in one click.
This isn't a replacement - it's a small helper that extends your workflow beyond the cloud. If it saves you even a little time, I'll consider it a win.
Supported Formats
Convert NDJSON to COCO JSON, Pascal VOC, and all YOLO versions for local training.
YOLO26 (latest)
TXT annotations and YAML config used with YOLO26.
YOLOv12
TXT annotations and YAML config used with YOLOv12.
YOLO11
TXT annotations and YAML config used with YOLO11.
YOLOv9
TXT annotations and YAML config used with YOLOv9.
YOLOv8
TXT annotations and YAML config used with YOLOv8.
YOLOv7
TXT annotations and YAML config used with YOLOv7.
YOLOv5
TXT annotations and YAML config used with YOLOv5.
YOLO Darknet
Darknet TXT annotations used with YOLO Darknet (both v3 and v4) and YOLOv3 PyTorch.
COCO JSON
COCO JSON annotations are used with EfficientDet Pytorch and Detectron 2.
Pascal VOC
Common XML annotation format for local data munging (pioneered by ImageNet).
TFRecord
Coming SoonTFRecord binary format used for both Tensorflow 1.5 and Tensorflow 2.0 Object Detection models.
CreateML
Coming SoonCreateML JSON format is used with Apple's CreateML and Turi Create tools.
How to Convert Ultralytics NDJSON to YOLO
Three steps. One ZIP file. Done.
Select Your NDJSON
Pick your .ndjson or .jsonl export file from your YOLO's project.
Choose a Format
Select from 12 target formats including YOLO's, COCO, Pascal VOC, and more.
Download Your ZIP
Get a complete ZIP with converted annotations, images, and config files.
Built for Speed & Privacy
For ML engineers who need to move fast between frameworks.
Fast Downloads
100 concurrent connections download your images in parallel. Built with Rust and Tokio for maximum throughput.
12 Formats, 5 Task Types
From YOLO's to COCO JSON to Pascal VOC. Supports detection, segmentation, pose estimation, OBB, and classification.
100% Private
Everything runs on your machine. No data is ever sent to external servers. Your annotations stay yours.
Frequently Asked Questions
Common questions about converting Ultralytics NDJSON exports