Lossless Compression Lab

Ten classic lossless coders, each one a real encoder and decoder. Every size below is the length of an actual bit stream, with headers and code tables counted, and every stream is decoded again and compared with the input byte for byte. Try some presets, paste text, or drop in a file (up to 256 KiB).

Presets:

Open file… …or drop a file anywhere on this box.

Scoreboard

Bits per input byte: lower is better, and 8 means no compression at all. The dashed line is the order-0 entropy H₀: the bound for any coder that treats bytes as independent draws from the input's own histogram, without paying for the table. Coders that model context or repetition can beat it. Click a row for details.

Single self-contained page, no dependencies. Codec logic lives in the shared-code block and is tested by node test.mjs.