Google Cloud Vision API: 1,000 Free Units per Month (Text Detection / OCR and More)
Google Cloud
The first 1,000 units each month are free (counted per feature, including Text Detection OCR and Label Detection), long-term
Official pricing page: under the "First 1000 units/month" column, features such as Label Detection and Text Detection are marked "Free"; from the 1001st unit up to 5 million, billing is per 1,000 units (Text Detection is $1.50 per 1,000 units). Google Cloud's official free-tier list says: "Cloud Vision: 1,000 units per month". Each feature applied to an image counts as 1 unit.
1,000 units a month is enough only for small-scale trials. You need a Google Cloud project with billing enabled (credit card); usage beyond the free units is charged automatically, so set a budget alert. Users in mainland China need a proxy. For a domestic alternative see the Tencent Cloud OCR monthly free entry (1,000 calls per month).