Base64 Decode and Encode

Base64 Decode and Encode

Decode and Encode Base64 data with this free online Base64 Encoder and Decoder tool in real-time.

Created by Commontools | Updated on: June 23, 2022

What Is Base64 Encoding? How Does Base64 Encoding And Decoding Work?

Base64 encoding is the process of converting binary data into the ASCII string format, by converting the binary data into the character representation of 6-bits. It is the Base64 process of encryption is employed for binary data such as video or images and is transmitted through systems specifically designed to transmit information in plain-text (ASCII) form.

Encoding Base64 lets us convert binary or text data into ASCII characters. By encoding data, we increase the chance of it being properly processed by different systems.

In this article, we will discover how Base64 encodes and decodes and how to be utilized. We'll then apply Python for Base64 encoding and decoding binary and text data.

What exactly is Base64 Encoding?

Base64 encoding is a form which converts bits to ASCII characters. In mathematics, the basis of a system of numbers refers to how many characters represent numbers. The name for this encoding originates from the base definition in mathematics - 64 characters represent the numbers in Base64.

Base64 character set contains:

  • 26 uppercase letters

  • 26 lowercase letters

  • 10 numbers

  • + and/or / for the creation of New lines (some implementations might employ different characters)

When a system converts Base64 characters into binary, every Base64 character represents six bits of data.

A brief overview of Base64 Encoding

The requirement for Base64 encoders stems from the issues that arise when media is transferred in binary format and raw to systems that use text.

Because systems that use text (like emails) take binary information in a wide variety of characters, including special characters for command, a lot of the data transferred to media for transfer is misinterpreted by these systems and is lost or damaged during the process of transmission.

One way of encoding the digital data binary in a manner that doesn't cause transmission issues is to transmit it as simple ASCII data with a Base64 encoded form. This is among the methods employed to implement MIME. MIME standard to transmit information other than plain text.

Why do we use Base64 Encoding?

Computers transmit all information of various types is transmitted as 1s and 0s. However, certain communications channels and programs cannot comprehend the entirety of data they receive. This is due to the significance of the meaning of a sequence of 0s and 1s depending on the kind of data it is representing. For example, 10110001 needs to be handled differently depending on whether it is an image or a letter.

To circumvent this limitation, you could encode your data in text, which increases the probability of it being sent and processed properly. Base64 is one of the most popular methods to convert data that is binary transformed into ASCII characters and is well-known to the majority of applications and networks.

The most common scenario in which Base64 encoders are frequently used is on mail servers. They were initially designed to process text, but we expect to transmit images or other media along with the message. In these instances, your media information will be Base64 encoded at the time it's being transmitted. Then, it will be Base64 decoded once it is received, so that the application can make use of it.

Recognizing that data requires to be sent in a text to ensure that it doesn't get damaged, let's consider the ways we can utilize Python in order to Base64 encode data and then decode it.

Advantages of Using Base64 Encoding

The concept behind Base64 is quite simple.

Consider sending a message via binary. The message can be viewed as being composed of 8 bit characters. This is base256. Each bit represents a number between 0 and 255.

The issue with this code is that it can't be linked to emails or similar channels because certain characters are associated with a specific significance.

Instead of being able to use 8 bits digits, the Base64 code employs six bit words, i.e. 64 combinations. However, it converts these 64 digits into ASCII characters that range from "A" (meaning zero) to "/", which is 64.

The benefit is that it allows you to make use of the only legitimate ASCII characters that are fully compatible with every channel while minimizing the amount of waste. In reality, on seven bit-per-byte channel, there is only one lost bit. For 8 bits per byte, just two bits will be lost.

What is the procedure for Base64 Encoding work?

Base64 encoding uses the 65-character subset of the US-ASCII charset. Initial 64 characters from the subset of 65 characters have been transformed into a 6 bit binary sequence (26 = 64). The extra characters (is) are used to provide padding.

Each of the six-bit binary sequences ranging from 0 to the number 63 is assigned a Base64 alphabet. The mapping between the binary sequence and the Base64 alphabet is utilized during the encoding process.

The Base64 encoder receives the input of eight-bit bits. It processes data from the left side to the right and divides the input into groups of 24 bits by concatenating three 8-bit bits. These 24-bit groups are considered as four concatenated 6-bit groups. In the end, every 6-bit group is transformed into one character within the Base64 alphabet by referring to the previous Base64 alphabet table.

If the input contains less than 24 bits, no bits will be put in (on the left) to create the integral numbers of 6 bit groups. After that, the pads (equals) numbers are generated based on the next scenarios -

  • The final chunk of input is comprised of exactly 8 bits. 4 zero bits get combined to create two six-bit groups. The 6-bit groups are then converted into the final Base64 encoded character by using the Base64 index table. The two pad (equals) characters are added to the resultant output.

  • The final input has exactly 16 bits. Zero bits of data are combined to create three six-bit groups. The three groups of 6-bits are transformed into the Base64 alphabet. In the end, one pad (=) character is added to the final output.

Base64 Encoding Logic

Base64 encoding splits binary data into 6 bits comprising 3 full bytes. It encodes them as printed characters in the ASCII standard. It does this in two steps.

First, you need to break the binary string into 6-bit chunks. Base64 is a simple format that uses just six bits (corresponding to 26 64 characters) to ensure that encoded data is printable and accessible. The special characters in ASCII are utilized.

The characters (hence the name Base64) are composed of 10 numbers that include 26 lowercase characters and 26 uppercase characters, as well as the plus (+) sign (+) and the Forward Slash (/). Additionally, there is the 65th character, also known as a pad which is also known as the Equal sign. (=). This character is utilized when the last bit of binary data doesn't have the full six bits.

Decoding and Encoding of Base64 process

The Base64 encoder receives information in the format of 8-bit bytes. It processes information from the left and then organizes the input into groups of 24 bits by combining three 8-bit bytes. These 24-bit groups are classified as four concatenated 6 bit groups. Every 6-bit group is transformed into one character within the Base64 alphabet after consulting the previously mentioned Base64 alphabet table.

When the input contains less than 24 bits, the 0 bits will be put in (on one side) to create the integral numbers of six-bit groups. In the next step, either one or two pads (is) character outputs based on the following scenarios:

  • The input has eight bits left at the time of completion: 4 zero bits get combined to create two six-bit groups. Every 6-bit segment is transformed into the Base64 encoded character by using the Base64 index table. Following that, the two pads (is) characters are added to the final output.

  • The input has 16 bits left at the end. 2 zero bits will be added together to create three six-bit groups. The three groups of 6-bits are transformed into the Base64 alphabet. Then, only a single pad (=) character is added to the output.

Base64 Encoding Example

As an example, consider three ASCII numbers, 155 162, 233, and 155. These three numbers constitute a binary stream of 100110111010001011101001. Binary files, just like an image, have a Unicode stream of many hundreds or hundreds of thousands of ones and zeros.

A Base64 encoder begins by separating this binary stream into groups comprising six characters such as 100110 111010 001011 10101001. Each of these groupings is converted into figures 38 11 and 41.

A binary stream of six characters transforms from the binary (or the base-2) into decimal (base-10) characters by squaring every value represented by one within the binary sequence using the square of its location. Beginning on the left and moving to the left and beginning with zero, the numbers that are in the stream are 20, 21 2, then 22, 23, 24 2, then 25.

Another way to look at the issue. Beginning from the left, each place is worth 1, 2 4 8, 16, and 32. When the number contains one in the slot it is added to that value and if it's zero within the slots, then you don't. This binary string is converted to 38, which is the decimal number that is: 0*201 + 1*21 1*22 + 0*23 + + 1*25 = 0+2+4+0+32.

Base64 encoding is a method of converting the text into binary form and splitting it into six bits: 38, 58and 11 and 41.

In the end, these numbers are then converted into ASCII characters by using the Base64 Encoding Table. The 6-bit values in this instance translating into an ASCII pattern m6Lp.

Utilizing this table: Base64 tables for conversion

  • 38 is 38.

  • It's 58, which is 6

  • 11 is L

  • 41 is 41

The two-step procedure applies to the entire binary string encoded.

To ensure that the encoded data is properly printed and does not override any mail server's line length limit Newline characters are added to limit line lengths to 76 characters. These characters encode the rest of the data.

Base64 Encoding via URL and safe filename alphabets

RFC 4648 defines the Base64 encoder that can be described as URL as well as Filename Safe. This means that the output generated by this Base64 encoder can be safely transferred in URLs and in filenames.

This variation is a straightforward modification in this variant. It is a simple change to the Base64 alphabet. Since the characters + and / are used to define URLs and filenames, they're substituted with hyphens ("-")) or underscore (_)

Decoding Strings using Python

The process of decoding the Base64 string is basically reversed by the encoder. We convert it by decoding the Base64 strings into bits of data that are not encoded. Then, we convert the object that looks like bytes into an actual string.

In a brand new file, Write this code in the file:

Base64 import

base64_message = 'UHl0aG9uIGlzIGZ1bg=='

base64_bytes = base64_message.encode('ascii')

message_bytes = base64.b64decode(base64_bytes)

message = message_bytes.decode('ascii')


We need to get the base64 module installed. We encode our message to the form of a bytes-like object using encode('ASCII'). We then call the base64.b64decode method to decode base64_bytes and then store them in our message_bytes variables. Then, we convert message_bytes to create a string object message, which makes it accessible to humans.

This file can be run to check the output below:

$ python3

Python is a lot of fun

Now that we are able to encode as well as decode strings let's attempt at encoding binary data.


Base64 encoding is a common method of converting data in various binary formats into strings composed of ASCII characters. This is particularly useful when sending data to networks or other applications that are unable to process raw binary data but could handle text.

With Python, we can utilize the module base64 in order for Base64 to encode or decode binary text as well as binary data.

Also, don't forget to check our free online Base64 Encoder and Decoder tool.



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