Convert text to and from binary, hexadecimal, octal, and decimal ASCII. Free bidirectional converter with UTF-8 support, padding, separator, and grouping options.
A free bidirectional text encoder/decoder across binary, octal, hexadecimal, and decimal bases. Type "Hello!" and see "01001000 01100101 01101100 01101100 01101111 00100001" instantly. Paste binary, hex, or decimal codes and decode them back to text. Supports UTF-8 (multi-byte emoji, accented characters) and ASCII-only modes with non-ASCII warnings. Configurable separator (space, comma, newline, none), per-byte zero-padding, and digit-group spacing for human readability. Auto-detects direction (text vs encoded) with manual override. Educational sidebar explains bits, bytes, and UTF-8.
Computers store every character as a number, and every number as a sequence of bits (binary digits). The conversion you see in this tool is exactly what happens when your computer saves a text file: each character maps to a code (ASCII or UTF-8), each code is a byte, each byte is 8 bits. Text → binary conversion is useful for: educational (showing students what a character actually "looks like" to a computer), debugging (when a string contains invisible or unexpected characters, the binary reveals every byte), cryptography puzzles and CTF challenges (binary-encoded flags are a common challenge style), steganography (hiding messages bit-by-bit in images), and retro computing / embedded systems (where you might be hand-coding character sequences).
Computers in the 1960s used a patchwork of incompatible character encodings (EBCDIC, BCD, six-bit codes). ASCII, standardised in 1963 by the American Standards Association, gave the English-speaking world a common 128-character set — letters, digits, punctuation, and control characters. But ASCII only covered English. National extensions (ISO-8859-1 for Western Europe, Shift-JIS for Japanese, GB2312 for Chinese) created a maze of incompatibilities — opening a Russian email in a Greek-locale email client showed gibberish. Unicode, announced in 1991 and developed since, finally unified everything into a single codespace covering ~150K characters from every script. UTF-8, designed by Ken Thompson and Rob Pike in 1993, is the encoding that made Unicode practical: backward-compatible with ASCII (no migration cost for English users), variable-length (1-4 bytes per character), and efficient enough for the web. Today, 98%+ of all text on the web is UTF-8.
ASCII (American Standard Code for Information Interchange) defines codes 0-127 — basic English letters, digits, and punctuation. Each ASCII character is exactly 1 byte (8 bits). UTF-8 is a backward-compatible superset that covers every character in Unicode (~150K+ characters). ASCII characters take 1 byte in UTF-8, but accented Latin letters (é, ü) take 2 bytes, most CJK characters take 3 bytes, and emoji take 4 bytes. UTF-8 is the standard for modern web and software; ASCII-only is now mostly a legacy / compatibility mode.
A byte is 8 bits, and ASCII characters are stored as 1 byte each. So the binary representation of any ASCII character is exactly 8 binary digits (with leading zeros padded if the value is small). "A" is decimal 65, which is binary 01000001 (8 digits, padded). "z" is decimal 122 = 01111010. The padding option in this tool lets you toggle 8-digit padding off (showing minimum-length binary like 1000001 for "A") or on (the default, showing standard 01000001).
Emoji codepoints live above U+10000 in the Unicode range, which UTF-8 encodes using 4 bytes (4 × 8 = 32 binary digits). For example, 🔥 is U+1F525, which UTF-8 encodes as the byte sequence F0 9F 94 A5 (or in binary: 11110000 10011111 10010100 10100101). When you encode emoji-laced text in this tool, you'll see the byte count grow disproportionately to the character count.
The tool warns you in a yellow callout above the output. Common issues: extra characters that aren't 0 or 1, incomplete final byte (e.g., 7 digits instead of 8), or non-ASCII binary in ASCII mode. The decoder tries to be forgiving — strips whitespace and separators, normalises grouping, and recovers from short tokens — but truly broken input produces an empty or partial decode with a warning.
Octal is base 8, using digits 0-7. Each octal digit represents 3 binary digits, making it a compact human-readable form of binary (used for Unix file permissions: chmod 755 means rwxr-xr-x). Hex is base 16, using digits 0-9 and A-F; each hex digit represents 4 binary digits. Hex is the most common base for raw byte representation in programming. Binary is the underlying form. Decimal (base 10) is the value that humans read as numbers.
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