Why this tool is useful
Use netstrings for simple length-prefixed protocol examples where delimiters may appear inside the payload and byte boundaries must remain unambiguous.
Text & List Tools · runs locally
Netstring Text Encoder and Decoder
Frame one UTF-8 value as length:data, or decode a strict netstring whose declared byte length matches exactly.
Ready. Your working data stays in this browser.
How it works
The browser counts UTF-8 bytes rather than characters, writes a decimal length and verifies the colon, comma and exact byte boundary during decoding.
Practical example
Hello becomes 5:Hello, while the Unicode value Привет uses its 12-byte UTF-8 length rather than six visible letters.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.