YOLO Inference API

The YOLO Inference API allows you to access the YOLOv8 object detection capabilities via a RESTful API. This enables you to run object detection on images without the need to install and set up the YOLOv8 environment locally.

Inference API Screenshot Screenshot of the Inference API section in the trained model Preview tab.

Watch: Ultralytics HUB Inference API Walkthrough

API URL

The API URL is the address used to access the YOLO Inference API. In this case, the base URL is:

https://api.ultralytics.com/v1/predict

Example Usage in Python

To access the YOLO Inference API with the specified model and API key using Python, you can use the following code:

import requests

# API URL, use actual MODEL_ID
url = f"https://api.ultralytics.com/v1/predict/MODEL_ID"

# Headers, use actual API_KEY
headers = {"x-api-key": "API_KEY"}

# Inference arguments (optional)
data = {"size": 640, "confidence": 0.25, "iou": 0.45}

# Load image and send request
with open("path/to/image.jpg", "rb") as image_file:
    files = {"image": image_file}
    response = requests.post(url, headers=headers, files=files, data=data)

print(response.json())

In this example, replace API_KEY with your actual API key, MODEL_ID with the desired model ID, and path/to/image.jpg with the path to the image you want to analyze.

Example Usage with cURL

You can use the YOLO Inference API with client URL (cURL) by utilizing the curl command. Replace API_KEY with your actual API key, MODEL_ID with the desired model ID, and image.jpg with the path to the image you want to analyze:

curl -X POST "https://api.ultralytics.com/v1/predict/MODEL_ID" \
    -H "x-api-key: API_KEY" \
    -F "image=@/path/to/image.jpg" \
    -F "size=640" \
    -F "confidence=0.25" \
    -F "iou=0.45"

Passing Arguments

This command sends a POST request to the YOLO Inference API with the specified MODEL_ID in the URL and the API_KEY in the request headers, along with the image file specified by @path/to/image.jpg.

Here's an example of passing the size, confidence, and iou arguments via the API URL using the requests library in Python:

import requests

# API URL, use actual MODEL_ID
url = f"https://api.ultralytics.com/v1/predict/MODEL_ID"

# Headers, use actual API_KEY
headers = {"x-api-key": "API_KEY"}

# Inference arguments (optional)
data = {"size": 640, "confidence": 0.25, "iou": 0.45}

# Load image and send request
with open("path/to/image.jpg", "rb") as image_file:
    files = {"image": image_file}
    response = requests.post(url, headers=headers, files=files, data=data)

print(response.json())

In this example, the data dictionary contains the query arguments size, confidence, and iou, which tells the API to run inference at image size 640 with confidence and IoU thresholds of 0.25 and 0.45.

This will send the query parameters along with the file in the POST request. See the table below for a full list of available inference arguments.

Inference Argument	Default	Type	Notes
`size`	`640`	`int`	valid range is `32` - `1280` pixels
`confidence`	`0.25`	`float`	valid range is `0.01` - `1.0`
`iou`	`0.45`	`float`	valid range is `0.0` - `0.95`
`url`	`''`	`str`	optional image URL if not image file is passed
`normalize`	`False`	`bool`

Return JSON format

The YOLO Inference API returns a JSON list with the detection results. The format of the JSON list will be the same as the one produced locally by the results[0].tojson() command.

The JSON list contains information about the detected objects, their coordinates, classes, and confidence scores.

Detect Model Format

YOLO detection models, such as yolov8n.pt, can return JSON responses from local inference, cURL inference, and Python inference. All of these methods produce the same JSON response format.

Detect Model JSON Response

ultralyticscURLPythonJSON Response

from ultralytics import YOLO

# Load model
model = YOLO('yolov8n.pt')

# Run inference
results = model('image.jpg')

# Print image.jpg results in JSON format
print(results[0].tojson())

curl -X POST "https://api.ultralytics.com/v1/predict/MODEL_ID" \
    -H "x-api-key: API_KEY" \
    -F "image=@/path/to/image.jpg" \
    -F "size=640" \
    -F "confidence=0.25" \
    -F "iou=0.45"

import requests

# API URL, use actual MODEL_ID
url = f"https://api.ultralytics.com/v1/predict/MODEL_ID"

# Headers, use actual API_KEY
headers = {"x-api-key": "API_KEY"}

# Inference arguments (optional)
data = {"size": 640, "confidence": 0.25, "iou": 0.45}

# Load image and send request
with open("path/to/image.jpg", "rb") as image_file:
    files = {"image": image_file}
    response = requests.post(url, headers=headers, files=files, data=data)

print(response.json())

{
  "success": True,
  "message": "Inference complete.",
  "data": [
    {
      "name": "person",
      "class": 0,
      "confidence": 0.8359682559967041,
      "box": {
        "x1": 0.08974208831787109,
        "y1": 0.27418340047200523,
        "x2": 0.8706787109375,
        "y2": 0.9887352837456598
      }
    },
    {
      "name": "person",
      "class": 0,
      "confidence": 0.8189555406570435,
      "box": {
        "x1": 0.5847355842590332,
        "y1": 0.05813225640190972,
        "x2": 0.8930277824401855,
        "y2": 0.9903111775716146
      }
    },
    {
      "name": "tie",
      "class": 27,
      "confidence": 0.2909725308418274,
      "box": {
        "x1": 0.3433395862579346,
        "y1": 0.6070465511745877,
        "x2": 0.40964522361755373,
        "y2": 0.9849439832899306
      }
    }
  ]
}

Segment Model Format

YOLO segmentation models, such as yolov8n-seg.pt, can return JSON responses from local inference, cURL inference, and Python inference. All of these methods produce the same JSON response format.

Segment Model JSON Response

ultralyticscURLPythonJSON Response

from ultralytics import YOLO

# Load model
model = YOLO('yolov8n-seg.pt')

# Run inference
results = model('image.jpg')

# Print image.jpg results in JSON format
print(results[0].tojson())

curl -X POST "https://api.ultralytics.com/v1/predict/MODEL_ID" \
    -H "x-api-key: API_KEY" \
    -F "image=@/path/to/image.jpg" \
    -F "size=640" \
    -F "confidence=0.25" \
    -F "iou=0.45"

import requests

# API URL, use actual MODEL_ID
url = f"https://api.ultralytics.com/v1/predict/MODEL_ID"

# Headers, use actual API_KEY
headers = {"x-api-key": "API_KEY"}

# Inference arguments (optional)
data = {"size": 640, "confidence": 0.25, "iou": 0.45}

# Load image and send request
with open("path/to/image.jpg", "rb") as image_file:
    files = {"image": image_file}
    response = requests.post(url, headers=headers, files=files, data=data)

print(response.json())

Note segments x and y lengths may vary from one object to another. Larger or more complex objects may have more segment points.

{
  "success": True,
  "message": "Inference complete.",
  "data": [
    {
      "name": "person",
      "class": 0,
      "confidence": 0.856913149356842,
      "box": {
        "x1": 0.1064866065979004,
        "y1": 0.2798851860894097,
        "x2": 0.8738358497619629,
        "y2": 0.9894873725043403
      },
      "segments": {
        "x": [
          0.421875,
          0.4203124940395355,
          0.41718751192092896
          ...
        ],
        "y": [
          0.2888889014720917,
          0.2916666567325592,
          0.2916666567325592
          ...
        ]
      }
    },
    {
      "name": "person",
      "class": 0,
      "confidence": 0.8512625694274902,
      "box": {
        "x1": 0.5757311820983887,
        "y1": 0.053943040635850696,
        "x2": 0.8960096359252929,
        "y2": 0.985154045952691
      },
      "segments": {
        "x": [
          0.7515624761581421,
          0.75,
          0.7437499761581421
          ...
        ],
        "y": [
          0.0555555559694767,
          0.05833333358168602,
          0.05833333358168602
          ...
        ]
      }
    },
    {
      "name": "tie",
      "class": 27,
      "confidence": 0.6485961675643921,
      "box": {
        "x1": 0.33911995887756347,
        "y1": 0.6057066175672743,
        "x2": 0.4081430912017822,
        "y2": 0.9916408962673611
      },
      "segments": {
        "x": [
          0.37187498807907104,
          0.37031251192092896,
          0.3687500059604645
          ...
        ],
        "y": [
          0.6111111044883728,
          0.6138888597488403,
          0.6138888597488403
          ...
        ]
      }
    }
  ]
}

Pose Model Format

YOLO pose models, such as yolov8n-pose.pt, can return JSON responses from local inference, cURL inference, and Python inference. All of these methods produce the same JSON response format.

Pose Model JSON Response

ultralyticscURLPythonJSON Response

from ultralytics import YOLO

# Load model
model = YOLO('yolov8n-seg.pt')

# Run inference
results = model('image.jpg')

# Print image.jpg results in JSON format
print(results[0].tojson())

curl -X POST "https://api.ultralytics.com/v1/predict/MODEL_ID" \
    -H "x-api-key: API_KEY" \
    -F "image=@/path/to/image.jpg" \
    -F "size=640" \
    -F "confidence=0.25" \
    -F "iou=0.45"

import requests

# API URL, use actual MODEL_ID
url = f"https://api.ultralytics.com/v1/predict/MODEL_ID"

# Headers, use actual API_KEY
headers = {"x-api-key": "API_KEY"}

# Inference arguments (optional)
data = {"size": 640, "confidence": 0.25, "iou": 0.45}

# Load image and send request
with open("path/to/image.jpg", "rb") as image_file:
    files = {"image": image_file}
    response = requests.post(url, headers=headers, files=files, data=data)

print(response.json())

Note COCO-keypoints pretrained models will have 17 human keypoints. The visible part of the keypoints indicates whether a keypoint is visible or obscured. Obscured keypoints may be outside the image or may not be visible, i.e. a person's eyes facing away from the camera.

{
  "success": True,
  "message": "Inference complete.",
  "data": [
    {
      "name": "person",
      "class": 0,
      "confidence": 0.8439509868621826,
      "box": {
        "x1": 0.1125,
        "y1": 0.28194444444444444,
        "x2": 0.7953125,
        "y2": 0.9902777777777778
      },
      "keypoints": {
        "x": [
          0.5058594942092896,
          0.5103894472122192,
          0.4920862317085266
          ...
        ],
        "y": [
          0.48964157700538635,
          0.4643048942089081,
          0.4465252459049225
          ...
        ],
        "visible": [
          0.8726999163627625,
          0.653947651386261,
          0.9130823612213135
          ...
        ]
      }
    },
    {
      "name": "person",
      "class": 0,
      "confidence": 0.7474289536476135,
      "box": {
        "x1": 0.58125,
        "y1": 0.0625,
        "x2": 0.8859375,
        "y2": 0.9888888888888889
      },
      "keypoints": {
        "x": [
          0.778544008731842,
          0.7976160049438477,
          0.7530890107154846
          ...
        ],
        "y": [
          0.27595141530036926,
          0.2378823608160019,
          0.23644638061523438
          ...
        ],
        "visible": [
          0.8900790810585022,
          0.789978563785553,
          0.8974530100822449
          ...
        ]
      }
    }
  ]
}

Created 2024-01-23, Updated 2024-03-06
Authors: RizwanMunawar (1), glenn-jocher (3), priytosh-tripathi (1)

YOLO Inference API

API URL

Example Usage in Python

Example Usage with cURL

Passing Arguments

Return JSON format

Detect Model Format

Segment Model Format

Pose Model Format

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