The storage capacity for localStorage is typically 5MB per domain: 1) This limit is per origin (protocol + domain + port), 2) Different browsers might implement slightly different limits, 3) Chrome, Firefox, and Safari generally provide 5-10MB per domain, 4) The limit applies to the total size of all key-value pairs combined, 5) The size is calculated based on UTF-16 string encoding, 6) Attempting to exceed this limit triggers a QuotaExceededError, 7) Mobile browsers might have different (often lower) limits, 8) Developers should monitor storage usage and implement cleanup strategies when approaching limits.