Convert annotation formats

How to Convert COCO JSON to Segment Anything 2

In this guide, we show you how to convert data between the COCO and Segment Anything 2 formats for free. You can use your converted data to train models and other models that support the Segment Anything 2 format.

Convert with an AI agent

Paste this prompt into your coding agent

Claude Code, Cursor, Codex or any agent with the Roboflow MCP uploads your COCO JSON dataset to Roboflow, generates a version and downloads it as Segment Anything 2.

No Roboflow MCP yet? The prompt has your agent set it up first, or connect your agent before you paste it.

Rather convert it by hand? Follow the steps below

COCO JSON

COCO is a common JSON format used for machine learning because the dataset it was introduced with has become a common benchmark.

Below, learn the structure of COCO JSON.

coco.jsonJSON
{
    "info": {
        "year": "2020",
        "version": "1",
        "description": "Exported from roboflow.ai",
        "contributor": "Roboflow",
        "url": "https://app.roboflow.ai/datasets/hard-hat-sample/1",
        "date_created": "2000-01-01T00:00:00+00:00"
    },
    "licenses": [
        {
            "id": 1,
            "url": "https://creativecommons.org/publicdomain/zero/1.0/",
            "name": "Public Domain"
        }
    ],
    "categories": [
        {
            "id": 0,
            "name": "Workers",
            "supercategory": "none"
        },
        {
            "id": 1,
            "name": "head",
            "supercategory": "Workers"
        },
        {
            "id": 2,
            "name": "helmet",
            "supercategory": "Workers"
        },
        {
            "id": 3,
            "name": "person",
            "supercategory": "Workers"
        }
    ],
    "images": [
        {
            "id": 0,
            "license": 1,
            "file_name": "0001.jpg",
            "height": 275,
            "width": 490,
            "date_captured": "2020-07-20T19:39:26+00:00"
        }
    ],
    "annotations": [
        {
            "id": 0,
            "image_id": 0,
            "category_id": 2,
            "bbox": [
                45,
                2,
                85,
                85
            ],
            "area": 7225,
            "segmentation": [],
            "iscrowd": 0
        },
        {
            "id": 1,
            "image_id": 0,
            "category_id": 2,
            "bbox": [
                324,
                29,
                72,
                81
            ],
            "area": 5832,
            "segmentation": [],
            "iscrowd": 0
        }
    ]
}

Segment Anything 2

SAM-2 uses a custom dataset format for use in fine-tuning models. You can convert and export data to the SAM 2 format in Roboflow.

Below, learn the structure of Segment Anything 2.

JSON
{"image":{"image_id":3,"license":1,"file_name":"A2_jpg.rf.1aa89274b154e74a1f960fbb192c6bf2.jpg","height":416,"width":416,"date_captured":"2024-10-07T11:35:58+00:00"},"annotations":[{"id":3,"bbox":[92,153,193.077471,199.115617],"area":38444.7397669646,"segmentation":{"counts":"...","size":[416,416]}}]}

Step 1: Create a free Roboflow account

Roboflow is a universal conversion tool for computer vision annotation formats. To convert your dataset, start by creating a free Roboflow account.

Create free Roboflow account

Step 2: Upload your data into Roboflow

Once your account has been created, click Create New Project. (opens in a new tab)

Roboflow's create project form, with Object Detection selected as the project type

Upload your data to Roboflow by dragging and dropping your COCO JSON images and annotations into the upload space.

Roboflow's upload page, with a drag-and-drop area for images, annotations, videos and PDFs

Step 3: Generate Dataset Version

Next, click "Generate New Version" to generate a new version of your dataset:

Roboflow's Generate a Dataset Version page, showing the source images and train/test split for a new version

You can then apply any preprocessing or augmentation steps to your dataset:

The augmentation step of a new dataset version, with 90° Rotate and Brightness added

Step 4: Export Dataset Version

After generating, you will be prompted to Export your dataset. You can choose to receive your dataset as a .zip file or a curl download link. Choose Segment Anything 2 when asked in what format you want to export your data. You will see a dropdown with various options like this:

Roboflow's Download dialog, with the export format list open and COCO highlighted

Congratulations, you have successfully converted your dataset from COCO JSON format to Segment Anything 2 format!

Video Tutorial

Convert Computer Vision Annotation Formats Tutorial

Want to dive deeper into converting annotation formats with Roboflow? In the tutorial below, we explore how to convert your data in the Roboflow dashboard. We also discuss rejecting annotations and train-test-validation splits.

Frequently Asked Questions

Yes! It is free to convert COCO JSON data into the Segment Anything 2 format on the Roboflow platform.

If you have between a few and a few thousand images, converting data between these formats will be quick. But, the time it takes to convert between data formats increases with the more images you have.

Show guide

Convert COCO JSON to other formats

Convert other formats to Segment Anything 2

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