Base64 Encoder/Decoder

📖 Description

1. What is Base64 Encoding?

Base64 is a method for representing binary data using 64 printable characters. It is primarily used to transmit binary data (such as images, audio, encryption keys) over media that only support text content (like email, HTML, JSON, XML).

The 64 core characters used by Base64 include:

• Uppercase letters A-Z (26)
• Lowercase letters a-z (26)
• Digits 0-9 (10)
• Special symbols + and / (2)
• Additionally, = is used as padding at the end.

2. The Conversion Principle of Base64: 8-bit to 6-bit

The core logic of Base64 is to convert three 8-bit bytes (24 bits) into four 6-bit bytes (24 bits).

1. Grouping: Divide the binary data to be processed into groups of 3 bytes each (24 bits per group).
2. Splitting: Re-divide these 24 bits into 4 groups, each containing 6 bits.
3. Mapping: The 6 bits can represent values from $0$ to $63$. Based on this value, find the corresponding character in the Base64 index table.
4. Padding: If the number of bytes in the original data is not a multiple of 3, Base64 uses = for padding at the end. This is why many Base64 strings end with one or two = characters.

Note: After Base64 encoding, the data size typically increases by about 33% compared to the original data.

3. Main Features of This Tool

4. How to Use This Tool

1. Text Encoding/Decoding

• Input text → Click "Encode" to get Base64
• Input Base64 → Click "Decode" to restore the original text

2. Image Base64 Processing

• Upload an image to automatically convert it to Base64
• Paste a Base64 string to immediately display a preview of the image

3. Audio/Video Files

• Upload audio/video files
• The tool automatically generates Base64, which can be directly used for:
  • Web development
  • Mobile development
  • Embedded display
  • API transmission, etc.

4. Base64 Encoding for Any File

Such as PDF, ZIP, DOCX, EXE, etc.

Steps:

1. Select a file
2. Wait a moment
3. The tool generates a complete Base64 DataURL or pure Base64 string

5. Convert Base64 Back to a File

Suitable for:

• Restoring files provided by others as Base64
• Recovering Base64 data returned by an API
• Simply paste the Base64 string → Click "Restore File" to download.

5. Typical Application Scenarios for Base64

A. Image to Base64 (Data URI)

In frontend development, to reduce the number of HTTP requests, developers often convert small icons directly into Base64 strings and embed them in HTML or CSS.

• CSS Example: background-image: url("data:image/png;base64,iVBORw0KGgoAAA...");
• Advantage: Reduces loading requests, improves initial page rendering speed.

B. Email Transmission (MIME)

Early email systems were primarily based on ASCII and could not directly transmit binary images or attachments. Base64 converts attachments into plain text format, ensuring stable transmission between different mail servers.

C. URL-Safe Base64

Standard Base64 contains + and /, which get escaped during URL transmission. The tool provided on this site supports URL Safe mode, replacing these symbols with - and _, allowing them to be used directly as URL parameters without secondary encoding.

D. JSON and XML Data Transmission

When calling Web API interfaces, if non-text data (such as RSA public keys, binary file streams) needs to be transmitted, it is usually first converted into a Base64 string and nested within a JSON object.

6. Frequently Asked Questions (FAQ)

Q: Is Base64 an encryption method?

A: No. Base64 is only an encoding method. Anyone can restore the original data using a Base64 decoding tool. Its purpose is "facilitating transmission," not "data protection." If encryption is needed, please use the [AES] or [RSA] encryption tools provided on this site.

Q: Why does data become larger after Base64 encoding?

A: Because Base64 uses 4 characters to represent the original 3 bytes of data. Every 3 bytes of original data are encoded into 4 Base64 characters, so the size increases by a fixed ratio of about 1/3.

Q: What causes the "Invalid character" error during decoding?

A: This is usually because the string to be decoded contains characters outside the Base64 character set (such as spaces, special emojis, or incorrect line breaks). Please ensure the copied string is complete and free of interfering characters.

For Base fundamentals and encoding principles, see: Base64 Quick Start: Principles, Scenarios, Format, and Code Examples.

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