Your files stay on your device
Zstandard Decompress: Decode .zst In-Browser
Decode a .zst frame locally: magic checked before the decoder runs, expansion capped, encode refused with a reason (decoder-only build).
Decode only, on purpose: this build ships the zstandard decoder and no encoder: nothing half-ships. The magic bytes (28 B5 2F FD) are checked before the decoder runs, so wrong files fail with a name, not a crash.