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COCO JSON to YOLO Converter

Instantly convert standard COCO JSON bounding boxes (`[x_min, y_min, width, height]`) into normalized YOLO format (`class_id x_center y_center width height`). Downloads as a structured ZIP file ready for YOLOv8, YOLOv11, or YOLOv12 training.

Convert annotation format
Upload one annotation file and download it in a different format.

One file only

COCO JSON, YOLO TXT (ZIP), Pascal VOC XML, CVAT XML, LabelMe JSON, CSV, TSV, or JSONL.

Quick conversions

How COCO to YOLO Conversion Works

COCO JSON Format (Absolute Pixels)

COCO uses absolute pixel coordinates top-left origin:

"bbox": [x_min, y_min, width, height]
// Example on 1920x1080 image:
"bbox": [480, 270, 960, 540]

YOLO TXT Format (Normalized 0-1)

YOLO requires center coordinates normalized by image size:

<class_id> <x_center> <y_center> <width> <height>
// Converted:
0 0.500000 0.500000 0.500000 0.500000

Why use this online converter?

  • 100% Client-Side: Your dataset files never leave your browser.
  • Zero Category Skips: Automatically creates index mapping starting from 0.
  • ZIP Output: Generates individual .txt label files per image.
  • Ultralytics Ready: Compatible with YOLOv5 through YOLOv12.

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LabelOp supports AI-assisted annotation (SAM 2), dataset versioning, and universal exports.

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