Does this tool support Unicode and emoji?

Yes. This tool fully supports Unicode, including emoji (🎉), CJK characters (中文, 日本語, 한국어), accented letters (café, José), and any other UTF-8 text. It uses the TextEncoder API to convert input strings to UTF-8 bytes before Base64 encoding, and TextDecoder to convert decoded bytes back to a UTF-8 string. This ensures correct handling of multibyte characters that naïve btoa()/atob() calls would fail on.

What is Base64url encoding?

Base64url is a URL-safe variant of standard Base64. It replaces the + character with - (hyphen) and / with _ (underscore), and typically omits the = padding. This makes the encoded string safe to use in URLs, query parameters, filenames, and other contexts where +, /, and = have special meanings. Base64url is used in JWT tokens, URL-safe API tokens, and many modern web protocols. You can toggle URL-safe mode with the switch in the tool.

Is Base64 encryption?

No, Base64 is not encryption. It is an encoding scheme that provides zero security or confidentiality. Anyone with the Base64 string can instantly decode it — no key or password is needed. Base64 is designed for data transport, not data protection. If you need to protect data, use proper encryption algorithms like AES, RSA, or ChaCha20, and never rely on Base64 for security.

What's the maximum input size?

Since this tool runs entirely in your browser, the practical limit depends on your device's available memory. Most modern browsers can handle inputs of several megabytes without issues. However, because Base64 encoding expands data by ~33%, encoding very large strings will produce even larger outputs. For extremely large files (hundreds of MB), consider using a streaming approach or a server-side tool instead.

Can I encode binary files with this tool?

This tool is designed for text encoding and decoding, not binary files. For binary files (images, PDFs, archives), you would need to first read the file as an ArrayBuffer and then encode those bytes. The tool does display estimated decoded byte size and MIME type when decoding, which can be useful when working with Base64-encoded binary data from other sources.

Does it work on mobile devices?

Yes, this tool is fully responsive and works on all modern mobile browsers, including iOS Safari and Android Chrome. The layout adapts to smaller screens, and all features — encoding, decoding, URL-safe mode, copy, download, and swap — are available on mobile. The touch-friendly interface ensures a smooth experience on phones and tablets.

Is my data sent to a server?

No. This is a 100% client-side tool. All encoding and decoding happens in your browser using JavaScript. Your input text and Base64 strings never leave your device, are never sent to any server, and are not stored in any database. This makes the tool safe to use even with sensitive data like API keys, tokens, or credentials. Once you close or refresh the page, all data is gone.

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Base64 Encoder/Decoder

Encode text to Base64 and decode Base64 to text.

What is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that converts binary data into a sequence of printable ASCII characters. It is defined in RFC 4648 and uses a 64-character alphabet: the uppercase letters A–Z, lowercase letters a–z, digits 0–9, and the symbols + and /, with = used as padding when the input length is not a multiple of 3 bytes.

Here's how it works: every 3 bytes (24 bits) of input data are divided into four 6-bit groups. Each 6-bit group maps to one of the 64 characters in the Base64 alphabet. This means that 4 characters of Base64 output represent 3 bytes of original data, making Base64-encoded data approximately 33% larger than the original binary. When the input is not a multiple of 3 bytes, the output is padded with = characters to make the output length a multiple of 4.

Base64 is not encryption — it provides no confidentiality or security. Anyone who has the Base64 string can decode it instantly. Its purpose is to ensure that binary data can be safely transmitted over text-based protocols like HTTP, SMTP (email), and JSON, which may interpret certain byte sequences as control characters or modify them during transit. By encoding binary data as Base64, you guarantee that the data remains intact without modification.

A critical distinction is UTF-8 vs ASCII. The original Base64 specification was designed for arbitrary binary data. When encoding text strings, it is essential to first convert the text to UTF-8 bytes before Base64 encoding. This is because characters like emoji (🎉), CJK characters (中文), and accented letters (café) require multiple bytes in UTF-8. Naïvely calling btoa() on such strings without UTF-8 conversion will throw an error in browsers. Our tool correctly handles UTF-8 by using TextEncoder to convert the input string to UTF-8 bytes before encoding, ensuring full Unicode support including emoji, CJK, and all special characters.

Base64 encoding is used everywhere in modern web development: data URIs for embedding images directly in HTML or CSS, HTTP Basic Authentication headers, JWT (JSON Web Token) encoding, email MIME attachments, SAML assertions, and many API protocols. Understanding how Base64 works is essential for any developer working with web APIs, authentication systems, or data serialization.

How to Use Base64 Encoder/Decoder

Choose the mode: click Encode to convert text to Base64, or Decode to convert Base64 back to text.
If you need URL-safe output, toggle the URL-safe (Base64url) switch. This replaces + with - and / with _, and removes padding.
Type or paste your text (encode mode) or Base64 string (decode mode) into the input field. The tool processes your input automatically with a 200ms debounce.
View the result in the output field. The output is read-only and can be copied or downloaded.
Use the Copy button to copy the output to your clipboard, or Download to save it as a text file.
Click Swap to move the output into the input field and switch modes — handy for round-trip testing.
Click Load Example to try the tool with sample data.
Click Clear to reset both input and output fields.

Base64 vs Base64url

Base64url is a URL-safe variant of standard Base64, also defined in RFC 4648. Standard Base64 uses the characters + and /, which have special meanings in URLs and file paths. The + character represents a space in URL query strings, and / is a path separator. Additionally, the = padding character can cause issues in some URL contexts.

Base64url solves this by making three substitutions:

+ is replaced with - (hyphen)
/ is replaced with _ (underscore)
The = padding is typically omitted entirely

This makes Base64url-encoded data safe to use in URLs, filenames, and query parameters without any additional encoding. Base64url is used in JWT tokens, URL-safe API tokens, and many modern web protocols. Our tool supports both standard and URL-safe encoding — just toggle the switch to switch between them.

Common Use Cases

Data URIs — Embed small images, fonts, or files directly in HTML or CSS as data:image/png;base64,... URIs, reducing HTTP requests.
HTTP Basic Authentication — The Authorization: Basic header sends credentials as base64(user:pass).
JWT Tokens — JSON Web Tokens encode their header, payload, and signature using Base64url encoding.
Email MIME Attachments — Binary attachments in email are encoded as Base64 within MIME multipart messages.
API Tokens & Secrets — Many APIs return binary tokens (like OAuth refresh tokens) encoded as Base64 or Base64url strings.
SAML Assertions — Security Assertion Markup Language uses Base64 to encode XML assertions for browser-based SSO.
Source Maps — JavaScript source maps can embed original source content as Base64-encoded strings.

Features

Full Unicode support — correctly encodes and decodes emoji, CJK characters, accented letters, and all UTF-8 text
Dual mode — switch between Encode and Decode with a single click
URL-safe (Base64url) mode — toggle between standard and URL-safe encoding for use in URLs and filenames
Auto-processing — output updates automatically as you type (200ms debounce)
Base64 validation — real-time indicator shows whether your input is valid Base64
Copy to clipboard — one-click copy of the output for instant use
Download output — save the result as a text file
Swap input/output — instantly swap the result into the input and switch modes for round-trip testing
File info display — shows estimated decoded byte size and MIME type when decoding
Load example — try the tool instantly with built-in sample data
100% client-side — your data never leaves your browser; no server processing
Dark mode support — seamless experience in both light and dark themes

Frequently Asked Questions