Base64 Encoder / Decoder
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About this Tool
A full-featured developer utility that bidirectionally converts text strings and binary bytes into RFC 4648-compliant Base64 printable ASCII characters (A–Z, a–z, 0–9, +, /) and decodes Base64 payloads back to original text. Converting three 8-bit bytes (24 bits) into four 6-bit index characters, Base64 is the ubiquitous backbone of HTTP Basic Authentication headers, JSON Web Token (JWT) payloads, email MIME attachments, and inline image Data URIs. With full native UTF-8 support to eliminate legacy btoa() Latin-1 encoding exceptions, all operations execute 100% within your client-side browser sandbox without sending any sensitive credentials across the network.
Processed safely on your device
Everything happens in your browser on this device. Your files are never sent to our servers—so you can use it with peace of mind.
How to Use
Paste or type your plain text or Base64 string directly into the primary input editor.
Select your operation: 'Base64 Encode' to generate encoded text or 'Base64 Decode' to restore original data.
Optionally toggle between standard Base64 (+, /, =) and URL-safe Base64URL (-, _, no padding) modes.
Click the copy button to instantly copy the resulting Base64 string or decoded plain text to your clipboard for API headers or code.
Key Scenarios & Use Cases
HTTP Basic Authorization Header Generation
Encode 'username:password' credentials into Base64 format to construct standard 'Authorization: Basic ...' request headers for REST API testing.
JWT (JSON Web Token) Header & Payload Debugging
Quickly inspect, decode, and troubleshoot claims, issuer signatures, and expiration timestamps inside Base64URL-encoded JWT tokens.
HTML & CSS Inline Image Data URIs
Convert icons, logos, and badge graphics into 'data:image/png;base64,...' strings to eliminate external network requests in web templates and single-page apps.
Email MIME Attachment Inspection
Decode and verify raw Base64 attachment blocks embedded inside raw EML or RFC 822 email source messages.
Binary Tunneling via Text Channels
Safely pass cryptographic hashes, binary tokens, or serialized buffers through text-only network protocols, message queues (Kafka, RabbitMQ), or database text fields.
Frequently Asked Questions (FAQ)
Base64 takes three 8-bit bytes (24 bits of binary data) and splits them into four 6-bit groups (each representing a character from the 64-character table). Translating 3 bytes into 4 characters creates a mathematical size expansion of exactly 4/3, or roughly 33.3%.
Standard Base64 (RFC 4648 §4) uses '+' and '/', with '=' padding. In URLs, however, '+' represents a space and '/' is a path separator. Base64URL (RFC 4648 §5) substitutes '+' with '-' and '/' with '_', and omits padding '=' characters to make tokens safe for query strings and JWTs.
The native btoa() function is restricted to characters within the 1-byte Latin1 (0x00–0xFF) range. Multibyte characters like Korean, Japanese, or accented letters cause a 'Character out of range' exception. AllThatConverter first converts text into a standard UTF-8 byte array before encoding, supporting all Unicode characters flawlessly.
No. Base64 is strictly an encoding format, not encryption. There is no secret key or cryptographic security involved; anyone with a Base64 decoder can immediately retrieve the original data. Sensitive data must always be encrypted (e.g., using AES or RSA) before Base64 encoding.
Most modern decoders calculate length modulo 4 and decode successfully without padding. However, legacy systems, strict RFC parsers, or certain backend frameworks (like Java's java.util.Base64 without lenient mode) may throw an exception if padding is missing.
Yes, 100% secure. All encoding and decoding operations run locally within your browser's V8 JavaScript engine. No payload data is ever uploaded, cached, or logged on remote servers, and the tool functions without an internet connection.