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What is a SHA hash?
SHA-256, SHA-384, and SHA-512 belong to the SHA-2 family of cryptographic hash functions, standardized by NIST (FIPS 180-4). Each takes any input — text, a file's contents, anything — and produces a fixed-length "digest" that looks like random characters. The same input always produces the same hash, but there's no way to reverse a hash back into the original input. That makes hashes useful for verifying a file hasn't been altered (checksums), confirming data integrity, and as a building block in digital signatures and systems like Git and Bitcoin.
SHA-256 vs SHA-384 vs SHA-512: which should I use?
| SHA-256 | 256 bits (64 hex characters) | The most widely used and compatible default — this is what most checksums, APIs, and file-verification tools expect. |
| SHA-384 | 384 bits (96 hex characters) | A truncated variant of SHA-512, sometimes required by specific compliance or protocol standards. |
| SHA-512 | 512 bits (128 hex characters) | A larger security margin than SHA-256, and often faster on 64-bit systems — a good choice when you specifically need SHA-2's strongest option. |
Is it safe to hash sensitive data with this tool?
Yes — hashing happens entirely in your browser using the Web Crypto API. Nothing you type is ever uploaded, logged, or stored on a server.
What is SHA-256 used for?
Verifying downloaded files haven't been corrupted or tampered with, confirming data integrity, digital signatures, and as a core building block in systems like Git and Bitcoin. It is not, by itself, a good way to store passwords — use bcrypt, scrypt, or Argon2 for that.
Can I get the original text back from a hash?
No. Hashing is one-way by design — there is no way to reverse a SHA-256/384/512 hash back into the input that produced it.
SHA-256、SHA-384、SHA-512 之间有什么区别？
它们同属 SHA-2 家族，底层设计一致，主要区别在于输出长度和运算速度。SHA-256 输出 256 位，是使用最广泛的默认选项。SHA-512 输出 512 位，安全裕度更大，在 64 位系统上往往运算更快。SHA-384 是 SHA-512 内部运算的截断版本，输出 384 位，主要用于某些标准或协议明确要求这个长度的场景。日常用途（文件校验、完整性核对）用 SHA-256 就足够；如果你specifically想要 SHA-2 里安全裕度最大的选项，就选 SHA-512。
SHA-512 比 SHA-256 或 SHA-384 更安全吗？
从理论安全裕度来看，是的。对于 n 位的哈希，通用的碰撞抵抗力大约是 2^(n/2)——SHA-256 约为 2¹²⁸，SHA-384 约为 2¹⁹²，SHA-512 约为 2²⁵⁶，所以 SHA-512 的安全裕度最大。但实际使用中这个差距通常不重要：2¹²⁸ 已经远超现实中任何可行的计算量，而且 SHA-2 家族目前没有任何已知的实际可行攻击。日常使用 SHA-256 完全没问题；只有当你specifically需要更大的理论安全裕度，或者某个协议明确要求时，才需要选 SHA-512。