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Free tools

Practical tools for annotation and dataset workflows.

Start with practical tooling: clean format handoff, catch risky dataset patterns early, and remove friction before the next training run.

Annotation Format Converter
Convert one annotation file between COCO, YOLO, Pascal VOC, CVAT, LabelMe, and more.
Convert between COCO JSON, YOLO TXT, Pascal VOC XML, CVAT XML, LabelMe JSON, CSV, TSV, and JSONL.
  • No login required
  • Auto-detects source format
  • Quick conversion shortcuts for popular format pairs
  • ZIP output for per-image formats like YOLO and VOC
Format converter
Annotation Merger
Merge many annotation files and turn them into one download target.
Merge Pascal VOC XML, LabelMe JSON, YOLO TXT, COCO JSON, CVAT XML, CSV, TSV, or JSONL.
  • No login required for merge and download
  • ZIP or multi-file input
  • Per-image output when the target format needs it
  • Bounding-box-first conversion for mixed export pipelines
Annotation merger
Dataset Splitter
Split a COCO JSON file into train, validation, and test sets.
Upload one COCO JSON, set the split ratio, and download three ready-to-train files.
  • Runs entirely in your browser
  • Configurable train/val/test ratios
  • Stratified sampling to preserve class distribution
  • Download each split individually or all at once
Dataset splitter
Dataset Health Report
Check one annotation file for class imbalance, parse skips, and geometry risks.
Analyze COCO JSON, CVAT XML, JSONL, CSV, or TSV in one in-page report.
  • Single-file health report in-page
  • Class distribution and annotation density charts
  • Warnings for duplicates, empty images, and out-of-bounds boxes
  • Built for pre-training QA, not export conversion
Dataset health report
Label Mapper / Taxonomy Tool
Rename labels, merge synonyms, drop noisy classes, and assign taxonomy parents.
Upload one annotation file, audit the label set, preview mapping impact, and download a corrected export with optional class-map artifacts.
  • No login required
  • Smart suggestions for label variants and typos
  • COCO category remap with supercategory support
  • Optional label-map.json, classes.txt, and data.yaml
Label mapper

Popular Direct Format Converters

Direct links to specialized single-pair format conversion tools:

COCO → YOLO

Convert COCO JSON bboxes to normalized YOLOv8/v11 txt files.

YOLO → COCO

Merge multi-file YOLO labels into a unified COCO JSON dataset.

Pascal VOC → YOLO

Convert Pascal VOC XML bounding box coordinates to YOLO txt.

Frequently Asked Questions About LabelOp Tools

Are these tools free to use?

Yes, 100% free. There are no paywalls, subscriptions, or login requirements to convert, merge, split, or audit your annotation files.

Is my dataset uploaded to your servers?

No. All parsing, coordinate conversion, and analysis run locally in your browser using client-side JavaScript. Your images and labels never leave your machine.

Which YOLO versions are supported?

All Ultralytics YOLO versions (YOLOv5, YOLOv8, YOLOv9, YOLOv10, YOLOv11, YOLOv12) and darknet formats are fully supported with normalized coordinates.

Can I annotate directly in LabelOp?

Yes. LabelOp provides a complete AI-assisted labeling platform with SAM 2 smart segmentation, team review queues, and direct model training on cloud GPUs.