# hexString The digest rendered as a 64-character lowercase hexadecimal string. ``` var hexString: String { get } ``` ## Return Value A 64-character ASCII string. For raw byte access, use [`rawValue`](/documentation/OpenSSL/SHA256/SHA256Digest/rawValue). ## Discussion Each of the 32 bytes in [`rawValue`](/documentation/OpenSSL/SHA256/SHA256Digest/rawValue) is formatted as two hex digits with no separators, no `0x` prefix, and no uppercase characters — the form consumed by JSON payloads, URL path segments, log lines, Git object IDs, JWT payload fingerprints, and Nostr NIP-01 event IDs. Output length is always exactly 64 ASCII characters regardless of input size, because SHA-256 is a fixed-length digest per FIPS 180-4. The value is recomputed on each access; callers that need it hot in a tight loop should cache the result. > Note: The string matches the regex `[0-9a-f]{64}`. Use the > stricter `.allSatisfy(\.isHexDigit)` check only if you also > need to reject uppercase — Foundation’s `isHexDigit` accepts > both cases.