Full UTF-8 Multi-Byte Character Support
Accurately encodes and decodes accented characters, emojis, and international non-ASCII characters without character corruption.
Base64 Encode & Decode
Free online Base64 Encode and Decode tool. Convert text to Base64 and decode Base64 back to plain UTF-8 text with URL-safe support and complete client-side security.
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All processing happens locally in your browser.
How It Works & Methodology
Base64 is a group of binary-to-text encoding schemes defined in RFC 4648. It represents binary sequences in an ASCII string format by translating 8-bit bytes into a radix-64 representation.
Base64 is designed to transport binary data (such as images, file attachments, and encryption keys) across channels that only reliably handle plain text without corrupting data during transit.
How Base64 Encoding Works Step-by-Step
1. Every 3 bytes (24 bits) of raw data are divided into 4 chunks of 6 bits each.
2. Each 6-bit chunk has a numeric value ranging from 0 to 63, which indexes into the standard 64-character alphabet:
• Indices 0–25: A–Z
• Indices 26–51: a–z
• Indices 52–61: 0–9
• Index 62: + (plus)
• Index 63: / (slash)
• Padding: = (equal sign used when input is not a multiple of 3 bytes)
Because 3 bytes of raw binary data turn into 4 ASCII text characters, Base64 encoding increases data overhead size by exactly 33.3% (or 4/3).
Common Use Cases in Modern Software
- Data URIs (Inline Assets): Embedding small icons, SVGs, or PNGs directly inside HTML
<img src="data:image/png;base64,...">or CSS files. - API Payloads: Passing binary payloads (such as PDF files or cryptographic keys) securely within JSON and XML structures.
- Email Attachments (MIME): Standard protocol encoding to ensure binary files survive email transfer agents.
Frequently Asked Questions
Developer Scenario: Encoding HTTP Basic Authentication Credentials
An API developer needs to generate an authorization header value by encoding "username:secret_token" into Base64 format.
| Plain Text Input | admin_api:secret_token_2026 |
| Base64 Output | YWRtaW5fYXBpOnNlY3JldF90b2tlbl8yMDI2 |
💡 The resulting Base64 string can be used directly in the HTTP Authorization header: `Basic YWRtaW5fYXBpOnNlY3JldF90b2tlbl8yMDI2`.
How to use Base64 Encode & Decode
- 1
Paste your text or Base64 string into the input editor.
- 2
Select your desired operation: Encode to transform plain text into Base64, or Decode to convert Base64 back into readable text.
- 3
Copy the resulting output to your clipboard or download it directly as a text file.
Why use this tool?
100% Client-Side Privacy
All encoding and decoding happen purely inside your browser memory. No tokens, passwords, or files are sent over the network.
Instant Error Detection
Identifies malformed Base64 padding, illegal characters, and invalid byte sequences immediately with helpful error messages.
Frequently asked questions
Is Base64 an encryption algorithm?
No. Base64 is an encoding format (RFC 4648) designed for data transmission across systems that only support text. It provides no confidentiality because anyone can decode it instantly without a key.
How much overhead does Base64 encoding add?
Base64 encoding increases data size by exactly 33.3% (ratio of 4 encoded ASCII characters for every 3 raw bytes).
What is the difference between standard and URL-safe Base64?
Standard Base64 uses "+" and "/" characters, which have special meanings in URLs. URL-safe Base64 replaces them with "-" (hyphen) and "_" (underscore) to safely travel in URLs and filenames without percent-encoding.
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