Select standard Base64 or Base64url and retain or omit its canonical padding deliberately.
Limited to 512 KiB of bytes and 1 MiB of encoded text.
Decoder reports keep lowercase hexadecimal authoritative.
Explicit byte-to-text semantics
Standard Base64 uses + and / while Base64url replaces them with - and _. They are separate profiles, not interchangeable spellings.
Standard Base64 uses + and / while Base64url replaces them with - and _. They are separate profiles, not interchangeable spellings.
Three source bytes become four symbols. The unpadded option removes only terminal equals signs and never changes the alphabet implicitly.
Encoder text is converted with UTF-8 only after malformed surrogate pairs are rejected. Hex mode accepts exact byte pairs without 0x, spaces, or separators. Decoder hex is authoritative; a text preview appears only when the bytes are valid UTF-8.
The work starts only when you submit the form. Source text, byte values, and results stay in the current browser tab; Tool Swim does not upload them, log their content, save presets, or call a developer API.
Base16, Base32, Base64, and Base85 allow at most 512 KiB of source or decoded bytes and 1 MiB of encoded text. Bitcoin Base58 is limited to 4,096 bytes or 5,600 characters because generic radix conversion is quadratic.
