Is the SHA-512 generator free?
Yes. It is completely free to use, with no signup, no account, and no paywall.
Do I need to install anything?
No. It runs in any modern browser on desktop or mobile, with nothing to download and nothing to configure.
Does it stay local?
Yes. Hashing runs entirely in your browser, so the text you hash never leaves your device.
Is SHA-512 more secure than SHA-256?
In theory yes, in practice the distinction is meaningless for almost everyone. SHA-256 gives roughly 128 bits of collision resistance, which corresponds to about 2 to the power of 128 operations to break, a number so far beyond any conceivable computing capacity that doubling it changes nothing about your real risk. The reasons to pick SHA-512 are practical ones: it is often faster on 64-bit hardware, some standards mandate it, and it produces more output bytes if you are using it inside a key derivation function.
Why is SHA-512 faster than SHA-256 on my machine?
Because it was designed for 64-bit words. SHA-512 processes 1024-bit blocks using 64-bit arithmetic, so on any 64-bit CPU it moves through more data per round than SHA-256, which uses 32-bit words. The effect can be 30 to 50 percent in favour of SHA-512 in pure software. The picture flips entirely on 32-bit and embedded hardware, and modern x86 chips with the SHA-NI instruction set accelerate SHA-256 in hardware, which can put it back in front.
Can I hash passwords with SHA-512?
Not as a bare digest. Speed is a virtue in a checksum and a liability in a password hash, and a GPU will chew through billions of SHA-512 operations per second. What you may be thinking of is sha512crypt, the $6$ scheme used in Linux shadow files, which iterates SHA-512 thousands of times over a salted input. The iteration count and the salt do the work there, not the algorithm. For anything new, use Argon2id, scrypt, or bcrypt.
Should I truncate a SHA-512 hash to make it shorter?
Only if you understand exactly how much margin you are giving up. Truncating a 512-bit digest to, say, 64 bits leaves you with 32 bits of collision resistance, which means a collision is findable in seconds. If you need a shorter digest there are properly specified truncated variants, notably SHA-512/256, that use different initial values rather than a naive cut. Ad-hoc truncation is how content-addressing schemes end up with accidental collisions.
Does the text get uploaded?
No. Your browser's native Web Crypto implementation computes the digest on your device. Nothing is sent over the network and nothing is stored, which matters given how often people paste secrets and personal data into hashing tools.
Why does hashing a huge block of text take no longer than a short one?
It does take longer, but hashing is fast enough that you cannot perceive the difference at the scale of a text box. A modern CPU hashes hundreds of megabytes to a couple of gigabytes per second, so a few thousand characters is finished in microseconds. What stays constant is the output: 128 hex characters, regardless of whether the input was one letter or a whole book.