apify/crawlee · error · Error

Unsupported content type: ${contentType}

Error message

Unsupported content type: ${contentType}

What it means

Dataset.exportTo() only supports 'application/json' (and CSV via the CSV path); passing any other contentType reaches the terminal guard and throws. The content type determines how dataset items are serialized into the target key-value store.

Source

Thrown at packages/core/src/storages/dataset.ts:437

            const { stringify } = await import('csv-stringify/sync');

            const value = stringify([
                keys,
                ...items.map((item) => {
                    return keys.map((k) => item[k]);
                }),
            ]);
            await kvStore.setValue(key, value, { contentType });
            return items;
        }

        if (contentType === 'application/json') {
            await kvStore.setValue(key, items);
            return items;
        }

        throw new Error(`Unsupported content type: ${contentType}`);
    }

    /**
     * Save entire default dataset's contents into one JSON file within a key-value store.
     *
     * @param key The name of the value to save the data in.
     * @param [options] An optional options object where you can provide the target KVS name.
     */
    async exportToJSON(key: string, options?: Omit<DatasetExportToOptions, 'fromDataset'>) {
        await this.exportTo(key, options, 'application/json');
    }

    /**
     * Save entire default dataset's contents into one CSV file within a key-value store.
     *
     * @param key The name of the value to save the data in.
     * @param [options] An optional options object where you can provide the target KVS name.
     */

View on GitHub (pinned to dbe57fb09c)

Solutions

1. Use exactly 'application/json' for JSON export or 'text/csv' for CSV export.
2. Export as JSON and convert to the desired format yourself afterwards.
3. Validate/normalize any user-supplied content type against the supported set before calling exportTo.
4. Check the current crawlee docs for newly supported formats; upgrade if a needed format exists in a newer version.

Example fix

// before
await dataset.exportTo('out', kvStore, 'text/json'); // unsupported

// after
await dataset.exportTo('out', kvStore, 'application/json');

const SUPPORTED = ['application/json', 'text/csv'];
if (!SUPPORTED.includes(contentType)) {
    throw new Error(`Use one of ${SUPPORTED.join(', ')}`);
}
await dataset.exportTo(key, kvStore, contentType);

type SupportedContentType = 'application/json' | 'text/csv';
function isSupportedContentType(x: string): x is SupportedContentType {
    return x === 'application/json' || x === 'text/csv';
}

try {
    await dataset.exportTo(key, kvStore, contentType);
} catch (e) {
    if (e instanceof Error && e.message.startsWith('Unsupported content type')) {
        await dataset.exportTo(key, kvStore, 'application/json');
    } else throw e;
}

When it happens

Trigger: Calling dataset.exportTo(key, kvStore, 'text/csv' as any) or any misspelled/unsupported type string that is not application/json (or text/csv on the CSV path).

Common situations: Typo in the content type constant, expecting XML/NDJSON support that does not exist, or passing a variable holding an arbitrary MIME type from user input.

Related errors

• Data item${s}is not an object. You can push only objects int
• Data item${s}is not serializable to JSON. Cause: ${err.messa
• dataset.getData(): The response is too large for parsing. Yo
• Dataset.forEach/map/reduce() support only a "json" format.
• The "value" parameter must be a String, Buffer, ArrayBuffer,

AI-assisted analysis of apify/crawlee@dbe57fb09c (2026-08-30). Data as JSON: /api/errors/3c70d0104c05b55c. Report an issue: GitHub.