What are the limits on product tags?

Tags are a key-value structure and there is more than one limit. A tag key must match the pattern of letters, digits, underscore and hyphen only, and be between 1 and 20 characters. A product variant can carry at most 20 tag keys. Each key holds an array of 1 to 10 unique values, and each value can be at most 40 characters and cannot contain tab or newline characters. Exceeding any of these fails validation rather than truncating silently, so validate in your own pipeline before sending. Note also that tags on product parent level are deprecated and no longer used, so set tags on the variant.