About

Base64 encoding represents binary data using 64 printable ASCII characters (A - Z, a - z, 0 - 9, +, /). Octal (base-8) represents each byte as a 3-digit value from 000 to 377. This tool decodes the Base64 input into its raw byte sequence, then converts each byte to its octal representation. Misinterpreting encoding layers is a common source of data corruption in protocol debugging, firmware analysis, and legacy system integration. A single padding error in Base64 or an out-of-range octal triplet (> 377₈) silently produces garbage bytes.

The reverse path validates that every octal group maps to a value in the range [0, 255] before re-encoding to Base64. This tool assumes the Base64 input follows RFC 4648 standard encoding without URL-safe alphabet variants. It does not handle Base64url (- and _ substitutions). Pro tip: if your octal dump comes from a Unix od command, strip the address column before pasting.

Formulas

Base64 decoding recovers the original byte stream. Each byte B in the decoded stream is then converted to base-8:

O = padStart(B₁₀.toString(8), 3, "0")

where B₁₀ is the decimal value of the byte (0 ≤ B ≤ 255) and O is the resulting 3-digit octal string (000 - 377).

The full octal output is the concatenation of all O_i values separated by spaces:

Result = O₀ ⋅ O₁ ⋅ … ⋅ O_n−1

For reverse conversion (Octal → Base64), each octal triplet is parsed:

B = parseInt(O, 8)

The constraint 0 ≤ B ≤ 255 must hold. Values of O ≥ 400₈ (= 256₁₀) are invalid single-byte representations.

Where: B = byte value (decimal), O = octal triplet string, n = total number of decoded bytes.

Reference Data

ASCII Character	Decimal	Octal	Binary	Base64 Index
A	65	101	01000001	0
B	66	102	01000010	1
Z	90	132	01011010	25
a	97	141	01100001	26
z	122	172	01111010	51
0	48	060	00110000	52
9	57	071	00111001	61
+	43	053	00101011	62
/	47	057	00101111	63
= (pad)	61	075	00111101	-
NUL	0	000	00000000	-
Space	32	040	00100000	-
LF (newline)	10	012	00001010	-
CR	13	015	00001101	-
TAB	9	011	00001001	-
DEL	127	177	01111111	-
Ã (195)	195	303	11000011	-
ÿ (255)	255	377	11111111	-
Max Octal Byte	255	377	11111111	-
Min Octal Byte	0	000	00000000	-

Frequently Asked Questions

A single byte ranges from 0 to 255 in decimal, which is 000 to 377 in octal. Three octal digits are needed because 8³ = 512, which covers the full byte range. Zero-padding to 3 digits ensures unambiguous parsing when converting back - without it, the sequence "17" could mean byte 15 (017) or two separate values.

This tool uses RFC 4648 standard Base64 alphabet (A - Z, a - z, 0-9, +, /). The URL-safe variant replaces + with - and / with _ (RFC 4648 §5). If your input uses URL-safe encoding, replace - with + and _ with / before pasting. The tool will reject - and _ as invalid characters.

No. The maximum value of a single byte is 255₁₀ = 377₈. If you enter an octal triplet like 400 or higher in the Octal → Base64 direction, the tool flags it as out-of-range. Multi-byte octal representations (e.g., from Unix od with 2-byte or 4-byte words) are not supported; split them into individual byte octals first.

Base64 encodes 3 bytes into 4 characters. When the input byte count isn't divisible by 3, padding characters (= or ==) are appended. One = means 2 bytes were encoded in the last group; two == means 1 byte. The octal output reflects only the actual decoded bytes - padding does not produce extra octal triplets.

Yes. The tool decodes the Base64 string into raw bytes regardless of whether the original data was text or binary (images, executables, etc.). Each byte is converted to its 3-digit octal equivalent. However, pasting extremely large Base64 strings (over 100 KB of encoded text) may cause browser slowdowns since conversion runs on the main thread.

It should not, if the original Base64 was properly padded. The decoded byte count is deterministic: n bytes always re-encode to ⌈n/3⌉×4 Base64 characters with the correct padding. If your round-trip differs, the original input likely had missing or extraneous padding. This tool's atob() will still attempt decoding but may silently drop trailing bits.