//base-64.com
DecodeEncode
Client-sideUTF-8 SupportURL-Safe Mode

Base64 Decode

Decode Base64 strings to plain text instantly. All processing happens in your browser — no data leaves your device.

Base64 Input
0 chars
Decoded Text
0 chars

// WHAT IS BASE64

Base64 is a binary-to-text encoding scheme that represents binary data in an ASCII string format. It is used everywhere — from email attachments to data URLs in CSS.

// 64 CHARACTERS

64 Characters, Infinite Data

Base64 uses a set of 64 printable ASCII characters to represent any binary data. The alphabet consists of:

Uppercase letters A–Z (26)
Lowercase letters a–z (26)
Digits 0–9 (10)
Symbols + and / (2)

An optional 65th character (=) is used for padding at the end.

A
0
B
1
C
2
D
3
E
4
F
5
G
6
H
7
I
8
J
9
K
10
L
11
M
12
N
13
O
14
P
15
Q
16
R
17
S
18
T
19
U
20
V
21
W
22
X
23
Y
24
Z
25
a
26
b
27
c
28
d
29
e
30
f
31
g
32
h
33
i
34
j
35
k
36
l
37
m
38
n
39
o
40
p
41
q
42
r
43
s
44
t
45
u
46
v
47
w
48
x
49
y
50
z
51
0
52
1
53
2
54
3
55
4
56
5
57
6
58
7
59
8
60
9
61
+
62
/
63

// HOW ENCODING WORKS

01

Split into Bytes

Your text is converted into bytes. Each character becomes an 8-bit number.

M0x4D77
a0x6197
n0x6E110
02

Join the Bits

All bytes are concatenated into one long stream of bits.

01001101 01100001 01101110
03

Group by 6 Bits

The bit stream is divided into groups of 6 bits. Each group maps to one Base64 character.

010011
010110
000101
101110
04

Map to Characters

Each 6-bit group (0-63) maps to a character in the Base64 alphabet.

010011(19)T
010110(22)W
000101(5)F
101110(46)u
"Man" encodes toTWFu

// USE CASES

Data URLs

Embed small images directly in HTML or CSS without separate HTTP requests.

data:image/png;base64,iVBORw0KGgo...

Email Attachments

MIME encodes binary attachments as Base64 text so they can travel through text-only email systems.

APIs & Configuration

Store binary secrets, certificates, and keys in JSON configs, environment variables, and Kubernetes secrets.

// HISTORY

1980s

Base64 Concept Born

Base64 encoding concept emerged in early mail systems for transmitting binary data over text-only channels.

1987

MIME Proposed

MIME (Multipurpose Internet Mail Extensions) was proposed, solving the problem of transmitting non-text data in email.

1992

RFC 1341 Published

Base64 was formally standardized as part of MIME in RFC 1341, defining the 64-character alphabet we use today.

1997

Data URLs Implemented

Netscape Navigator 4 first implemented data: URLs, later standardized in RFC 2397 (1998), enabling inline resource embedding in HTML.

Today

Modern Web Usage

Base64 is ubiquitous — from JWT tokens to CSS embeddings, APIs, and WebSocket binary data handling.

// FAQ

Is my data sent to a server?

No. All Base64 encoding and decoding happens entirely in your browser using JavaScript. Your data never leaves your device.

Does this support UTF-8?

Yes! The encoder handles UTF-8 characters correctly, including international characters, emojis, and special symbols.

What about URL-safe Base64?

Enable the URL-Safe option to use - and _ instead of + and /. The decoder automatically handles both standard and URL-safe Base64 variants.