Frequently asked questions about setup and usage.

Image/audio/resource loading error while labeling

The most common mistake while resource loading is CORS (Cross-Origin Resource Sharing) problem or Cross Domain. When you are trying to fetch a picture from external hosting it could be blocked by security reasons. Go to browser console (Ctrl + Shift + i for Chrome) and check errors there. Typically, this problem is solved by the external host setup.

How to make pre-annotations & pre-labeling

You can import pre-annotated tasks into LS. Pre-annotations will be automatically shown on Labeling page. Prepare your tasks with predictions field which is very similar to completions and then import your tasks to LS. Read more about task format and predictions.

  "data": {
    "my_text": "This is great" 

  "predictions": [{
    "result": [{
      "from_name": "sentiment_class",
      "to_name": "message",
      "type": "choices",
      "value": {
        "choices": ["Positive"]

How to write your own machine learning backend

Read this page to start writing your own ML backend.