yEnc encoder and decoder

This yEnc encoder converts plain UTF-8 text into the low-overhead binary transfer format long used on Usenet, and decodes framed or raw yEnc payloads back to readable text. yEnc keeps almost every octet as a single printable or extended character after a fixed plus-forty-two offset, escaping only a tiny critical set so binary data rides NNTP article bodies with far less expansion than Base64. Use it free in the browser for Usenet tooling practice and article debugging, or call the API at $0.002 per successful request when pipelines need reproducible yEnc transforms in CI and backend services.

What yEnc is and what this tool returns

yEnc is a content-transfer style encoding designed so binary files can travel inside Usenet articles without the one-third size penalty of Base64. Each input byte is shifted by forty-two modulo two hundred fifty-six; only the critical values null, line feed, carriage return, and equals are escaped by prefixing an equals sign and adding sixty-four before emission. Encoders then insert soft line breaks so article lines stay near the classic one-hundred-twenty-eight character width, and they frame the body with a =ybegin line that carries size, optional line length, and a file name, plus a =yend trailer that often includes size and an IEEE CRC-32 checksum. This page always follows that contract for UTF-8 text: encode mode UTF-8 encodes your string, applies the offset and critical escapes, wraps lines, and emits headers with a computed CRC; decode mode strips control lines, ignores CR and LF in the body, reverses escapes, checks size and CRC when present, and rejects incomplete equals sequences instead of guessing. The JSON response includes result for the transformed string, mode echoing encode or decode, encoding fixed to yenc, size for the binary payload length, optional name and crc32, framed true when headers were used or detected, and input_bytes plus output_bytes so you can assert sizes in tests. There is no streaming path and no silent repair of broken yEnc: either the string is valid under these rules or the request fails with invalid_input. If you need opaque email-safe packing, prefer Base64 or quoted-printable endpoints; this landing is for the Usenet-oriented yEnc encoding that news clients and binary posters already expect.

How text, mode, name, and line are read and how results stay reproducible

Encode accepts any Unicode string, converts it with the platform TextEncoder to UTF-8 bytes, then emits a framed yEnc article fragment with uppercase CRC-32. After bytes are recovered, a fatal UTF-8 decode ensures binary garbage does not become mojibake text. The preferred payload field is text, with aliases input, value, and s so forms, query strings, and SDK clients can reuse the same contract without renaming columns. Mode defaults to encode and accepts decode explicitly; aliases op, direction, and action map to the same switch for scripts that already use those names. Optional name (aliases filename, file) is written on the =ybegin line when encoding and defaults to data.bin; it must not contain carriage returns, line feeds, or equals signs. Optional line (aliases line_length, linewidth) sets the body wrap width between thirty-two and five hundred twelve characters and defaults to one hundred twenty-eight, matching common yEnc practice. Decode accepts framed text with =ybegin and =yend or a raw body-only stream: a trailing incomplete equals escape, an equals followed by a line break, a size mismatch against the decoded byte count, or a CRC-32 mismatch all fail with a clear invalid_input message. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing yEnc tables yourself. Invalid inputs return invalid_input and are not charged, which keeps validation cheap while successful transforms remain a fixed item price.

Where yEnc fits in Usenet, binaries, and test fixtures

Educators use the same tool when teaching the difference between Base64 opacity and yEnc’s low-overhead Usenet encoding for mostly binary payloads. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the encoded result.