HumanSignal/label-studio · error · ValidationError

{ext} extension is not supported

Error message

{ext} extension is not supported

What it means

ValidationError raised by check_extensions in label_studio/data_import/uploader.py. For each uploaded file, the extension (from os.path.splitext, lowercased) must appear in settings.SUPPORTED_EXTENSIONS (e.g. .csv, .json, .txt, .tsv); otherwise the upload is rejected because Label Studio cannot parse it into tasks.

Source

Thrown at label_studio/data_import/uploader.py:63

    # max tasks
    if len(tasks) > settings.TASKS_MAX_NUMBER:
        raise ValidationError(
            f'Maximum task number is {settings.TASKS_MAX_NUMBER}, current task number is {len(tasks)}'
        )


def check_tasks_max_file_size(value):
    if value >= settings.TASKS_MAX_FILE_SIZE:
        raise ValidationError(
            f'Maximum total size of all files is {settings.TASKS_MAX_FILE_SIZE} bytes, current size is {value} bytes'
        )


def check_extensions(files):
    for filename, file_obj in files.items():
        _, ext = os.path.splitext(file_obj.name)
        if ext.lower() not in settings.SUPPORTED_EXTENSIONS:
            raise ValidationError(f'{ext} extension is not supported')


def check_request_files_size(files):
    total = sum([file.size for _, file in files.items()])

    check_tasks_max_file_size(total)


def create_file_upload(user, project, file):
    instance = FileUpload(user=user, project=project, file=file)
    if settings.SVG_SECURITY_CLEANUP:
        content_type, encoding = mimetypes.guess_type(str(instance.file.name))
        if content_type in ['image/svg+xml']:
            clean_xml = allowlist_svg(instance.file.read().decode())
            instance.file.seek(0)
            instance.file.write(clean_xml.encode())
            instance.file.truncate()
    instance.save()

View on GitHub (pinned to 0b49e9b539)

Solutions

1. Convert the file to a supported format (.csv, .tsv, .json, or .txt) before upload.
2. If it's a text file without extension, rename it to include .txt/.csv/.json.
3. Extend settings.SUPPORTED_EXTENSIONS if you genuinely need the extension and have a converter path.
4. Unzip archives locally and upload the contained supported files one by one.

Example fix

// before
const fd = new FormData();
fd.append('file', new File([data], 'export.xlsx'));

// after
csv = xlsxToCsv(data);
fd.append('file', new File([csv], 'export.csv'));

import os
SUPPORTED = {'.csv', '.tsv', '.txt', '.json'}
for f in files:
    _, ext = os.path.splitext(f.name)
    if ext.lower() not in SUPPORTED:
        raise ValueError(f'{f.name}: {ext} not supported — convert to csv/tsv/txt/json first')

try:
    upload(files)
except ValidationError as e:
    if 'extension is not supported' in str(e):
        ext = e.message.split()[0]
        converted = [to_csv_or_json(f) for f in files if not supported(f)]
        upload(converted)
    else:
        raise

When it happens

Trigger: POSTing a file upload to the import API (create_file_uploads -> check_extensions) with a file whose extension is not in SUPPORTED_EXTENSIONS — e.g. .xlsx, .parquet, .zip, or a file with no extension.

Common situations: Uploading Excel or parquet files directly; zipped datasets; files saved without an extension; a deployment where SUPPORTED_EXTENSIONS was narrowed by config; misnamed files like data.json.txt being treated as .txt.

Related errors

• Maximum task number is {settings.TASKS_MAX_NUMBER}, current
• Maximum total size of all files is {settings.TASKS_MAX_FILE_
• extract_message(e)
• load_tasks: Data root must be list
• load_tasks: No tasks added

AI-assisted analysis of HumanSignal/label-studio@0b49e9b539 (2026-08-29). Data as JSON: /api/errors/0044d15c6f625f7c. Report an issue: GitHub.