Binary Encode / Decode
Turn UTF-8 text into space-separated 8-bit binary, or decode binary back to text. Runs in your browser. Nothing is uploaded.
How to use Binary Encode / Decode
- Paste or type UTF-8 text into Input and click Encode for space-separated 8-bit groups, or paste binary and click Decode to recover the original text.
- Encoded output looks like
01001000 01101001: eight bits per UTF-8 byte, separated by spaces. Decoding accepts the same layout, comma or newline separators, or one continuous stream of 0s and 1s whose length is a multiple of eight. - Use Swap in ↔ out to move a result back into the input for another round trip, Copy output for the clipboard, or Clear to reset both fields.
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What binary text encoding is for
Computers store text as bytes. Showing those bytes as binary (base-2) is a teaching and debugging habit: you can see how UTF-8 expands emoji into multiple bytes, check a homework worksheet, or explain why “one character” is not always “one byte”. This tool is deliberately simple: encode, decode and copy, with no file upload and no server round trip.
Typical jobs include classroom demos, verifying a hand-written bit string, or comparing side-by-side with Base64 Encode / Decode when you need a denser ASCII form of the same bytes. For puzzle-style text toys, see Morse Code and Upside-down Text.
UTF-8, groups and errors
Text is encoded with the browser’s UTF-8 TextEncoder, so accented letters and emoji become the correct multi-byte sequences before each byte is printed as eight bits. Decoding reverses that path with a strict UTF-8 decoder: if the bit groups form illegal UTF-8, you get a clear error instead of mojibake.
Invalid input is handled quietly: non-binary characters, groups longer than eight bits, or a total length that is not a multiple of eight produce an error status and an empty output. Short groups (fewer than eight bits) are left-padded with zeros so classroom snippets like 1001000 still decode as a full byte when that is what you meant.
Privacy and browser support
All work happens in your browser. Catpool does not receive, log or store the text you convert. Refresh the page to clear the fields. Modern desktop and mobile browsers with TextEncoder / TextDecoder are supported; there is no CDN and nothing to install.
FAQ
Is this the same as “binary code” for letters A=01000001?
For basic English letters in UTF-8 (which matches ASCII for A–Z), yes, A is 01000001. Accented characters and emoji use multi-byte UTF-8, so one visible character can become several 8-bit groups.
Why did decode fail?
Usually a typo (a digit other than 0 or 1), a truncated group, or bits that are not valid UTF-8. Fix the groups and try again; the status line explains the failure.
Can I encode a whole file?
This page is aimed at text in a textarea. Very large pastes may slow the tab; keep classroom and debugging snippets reasonably short.
Do you store what I paste?
No. Encoding, decoding and copy all stay on your device.
How is this different from Base64?
Base64 packs bytes into a shorter ASCII alphabet for transport. Binary here shows the raw bits for learning and inspection. Use whichever matches the job.
Related: Catpool home, Developer, Upside-down Text, Morse Code, Text Cleaner.
