Encoders and decoders.

The encoders and decoders cover 8 alphabets: Base64, Base32, Base36, Base58, Base62, Base85, hex and binary, each as an encoder, a decoder, a file encoder and a decoder that writes a file (32 pages). Base64 is the default for email, JSON and data URIs; hex is for reading bytes.

Base64 uses + and /, and pads with =. The URL-safe form uses - and _ and leaves the padding off, so it can sit in a URL or a file name unescaped. The Base64 encoder has a toggle for it, and the decoder reads either.

No. Every alphabet here only changes how bytes are written, so anyone can decode them with no key. Encrypt first when content needs protecting, then encode the ciphertext if it has to travel as text.

Base58 is Bitcoin's alphabet, with 0, O, I and l left out so that a hash or address is hard to misread and survives being read aloud. It is written as one big number, so it suits short values rather than files.

Base85 packs 4 bytes into 5 characters, a quarter longer than the input against Base64's third, and is the form PostScript and PDF use. It needs characters that aren't safe in URLs or JSON strings, so Base64 remains the common choice.

Text is turned into UTF-8 bytes before encoding, the encoding every language and command line uses by default, so accents, other scripts and emoji decode back to the same characters.

Use the file-to pages, such as File to Base64: drop any file and it is read in your browser and encoded, then copied or downloaded as a text file.

Use the to-file pages, such as Base64 to file. They decode the text to bytes, name the download after the format the first bytes suggest (PNG, JPEG, PDF, ZIP and others, or .bin when unknown), show a preview when it is an image, and let you rename the file.

The decoder shows replacement characters and says in the status line that the bytes aren't UTF-8 text. That usually means the data is a file, so the matching to-file page downloads the real bytes.

Yes: the Base64 decoders drop a data:...;base64, prefix before decoding, so you can paste a whole data URI. Other alphabets don't know the prefix.

Hex is twice the size of the bytes, binary eight characters a byte (nine with spaces), Base32 60 percent longer, Base64 about a third longer, Base85 a quarter longer. Base36, Base58 and Base62 land between 1.34 and 1.55 characters per byte.

Base36, Base58 and Base62 treat the input as one big number, which takes quadratic time, so they take up to 512 KB at once. The other alphabets set no size limit in the tool, and the browser's memory is the ceiling.

The status line under every encoding shows the bytes in, the characters out and the percentage longer, so you can see the cost of a choice on your own data before you pick one.

Because Base64 writes every 3 bytes as 4 characters, which is about a third longer than the file. That is why a Base64 data URI suits small icons better than photos.

The decoder found a character outside the alphabet, and names the first one. Base64 allows A to Z, a to z, 0 to 9, + and / (or - and _), Base32 A to Z and 2 to 7, and hex 0 to 9 and a to f. Spaces and line breaks are ignored.

Hex needs two digits for every byte, so an odd count means one is missing or extra. Binary needs eight digits for every byte, and the message gives the digit count it found.

A Base64 group can't be a single character, so input cut short that way is refused. Check that the whole string was copied and that nothing was added to it. Base85 refuses a final group of one character for the same reason.

Padding is optional: the Base64 and Base32 decoders accept it with or without the = signs. Mixing the two Base64 alphabets in one string is accepted as well, so a missing = is never the reason for an error.

No. Encoding and decoding run in your browser, in the page's own code, and the tool makes no network request with your input.

No. The encoders and decoders work without signing in, and nothing you type or drop is kept after you close the tab.

Once the page has loaded, yes: the alphabets are implemented in the page's code, with no library to fetch or server to ask, so the tool keeps working with the network off.