String → Base64
Encoder / Decoder

About Base64 Encoder & Decoder Tool

This free online Base64 encoder and decoder tool allows you to convert strings to Base64 encoding and decode Base64 back to original text instantly. Whether you're a developer working with APIs, encoding authentication tokens, transmitting binary data as text, or debugging Base64-encoded payloads, our bidirectional converter handles UTF-8 text, JSON objects, JWT tokens, API keys, and special characters with full Unicode support. Choose between standard Base64 or URL-safe Base64 encoding. Everything runs 100% in your browser with instant processing and batch conversion support.

Why Use Base64 Encoding?

Base64 encoding converts binary data or text into ASCII characters (A-Z, a-z, 0-9, +, /, =) that can be safely transmitted over text-based protocols like HTTP, email, JSON, and XML. It's essential for encoding authentication tokens (Basic Auth, JWT), transmitting binary files as text (images in data URLs, email attachments), storing binary data in JSON or XML, encoding URL parameters with special characters, transmitting encrypted data, embedding images in CSS or HTML, and ensuring data integrity across systems that don't handle binary data. Without Base64 encoding, binary data or special characters can be corrupted during transmission, cause parsing errors in text formats, break URL parameters, or fail authentication protocols. Base64 ensures safe, reliable data transport in text-only environments.

How to Use This Tool

Choose your conversion direction: String → Base64 mode encodes plain text, JSON, tokens, or any UTF-8 string into Base64 format—optionally enable URL-safe encoding (replaces + with -, / with _, removes padding) for use in URLs and filenames. Base64 → String mode decodes Base64-encoded strings (standard or URL-safe) back to original UTF-8 text. Paste your content into the input field (one item per line for batch processing), click Encode or Decode, and get instant results. Copy to clipboard for immediate use, download as a text file, or use the swap button to reverse the conversion and decode what you just encoded.

Key Benefits

• No installation required: Works directly in your browser without any software downloads
• Completely free: No registration, credit card, or hidden fees
• Secure and private: All encoding happens locally - your data never reaches our servers
• Fast processing: Instant encoding and decoding with no waiting time
• Bidirectional: Encode String → Base64 or decode Base64 → String with one click
• URL-safe option: Standard (+/=) or URL-safe (-_, no padding) Base64 encoding
• Full Unicode support: Handles UTF-8, emoji, Cyrillic, Chinese, Arabic, all languages
• Batch processing: Convert multiple strings or Base64 values simultaneously (one per line)

Common Use Cases

Developers use Base64 encoding for creating HTTP Basic Authentication headers (username:password encoded), encoding JWT tokens and OAuth credentials for APIs, generating data URLs for inline images (data:image/png;base64,...), encoding file uploads in JSON payloads, transmitting binary data over REST APIs, encoding email attachments in MIME format, storing binary data in databases or JSON files, encoding URL parameters with special characters safely, debugging API responses containing Base64 data, creating secure tokens for password reset links. Backend engineers encode configuration secrets, API keys, and encryption keys for storage and transmission, decode Base64-encoded request bodies and authorization headers, process file uploads sent as Base64, handle email attachments and embedded images. Frontend developers embed inline images in CSS and HTML, encode form data for submission, decode Base64 image previews, handle file upload responses. Security engineers work with encoded credentials, encrypted tokens, and obfuscated data for testing and auditing.

Standard vs URL-Safe Base64

Standard Base64 uses characters A-Z, a-z, 0-9, +, /, and = for padding. However, + and / have special meanings in URLs (+ becomes space, / is path separator) and = can cause issues in some contexts. URL-safe Base64 replaces + with -, / with _, and removes padding (=) to create strings safe for URLs, filenames, and query parameters. Use standard Base64 for HTTP headers, email attachments, JSON/XML data, and general encoding. Use URL-safe Base64 for JWT tokens in URLs, query parameters with encoded data, filenames and file paths, OAuth state parameters, and any scenario where + / = characters would be problematic. Our tool supports both formats with automatic detection during decoding.

Supported Features

String to Base64 encoding handles UTF-8 text with full Unicode support (all languages, emoji, special characters), JSON objects and arrays, API tokens and keys, multiline text and strings with line breaks, binary-like data represented as strings, and generates standard or URL-safe Base64 output. Base64 to string decoding automatically detects standard and URL-safe Base64 formats, handles both padded and unpadded Base64, correctly decodes UTF-8 multibyte characters, validates Base64 syntax and reports clear errors, preserves original text including newlines and special characters. Batch mode processes multiple strings or Base64 values (one per line) simultaneously, maintaining order and providing line-by-line conversion.

Technical Features

The encoder uses browser-native btoa/atob with UTF-8 handling via TextEncoder/TextDecoder for proper Unicode support, correctly encodes multibyte characters (2-4 bytes for Unicode), generates RFC 4648 compliant Base64 output, supports both standard (RFC 4648 §4) and URL-safe (RFC 4648 §5) variants, handles line breaks and special characters properly, validates Base64 syntax during decoding with detailed error messages, and processes large texts efficiently. The tool includes copy-to-clipboard, download options, swap functionality for roundtrip testing, and clear error reporting for invalid Base64 input (wrong characters, incorrect padding, malformed strings). Works reliably across all modern browsers with consistent results.

Privacy and Security

Unlike online Base64 converters that upload your data to remote servers, this tool processes everything locally in your browser using JavaScript. Your API keys, authentication tokens, JWT payloads, passwords, encryption keys, OAuth credentials, sensitive JSON data, or any text content never leave your computer, making it completely safe for encoding production secrets and confidential data. No cookies, tracking, data storage, or server communication. Perfect for working with production API tokens, user credentials, encrypted payloads, authentication headers, or any sensitive strings that require strict privacy controls. Your data remains 100% private and secure on your device. Note: Base64 is encoding, not encryption—it provides no security, only safe text representation of binary data.