Base64 Encoder / Decoder
Encode text to Base64 or decode Base64 back to text. Supports URL-safe encoding. 100% client-side.
Input — Plain Text
Output — Base64
How It Works
Bidirectional
Encode text to Base64 or decode Base64 back to plain text with one click.
URL-Safe Mode
Enable URL-safe encoding that replaces + with - and / with _ for use in URLs.
No Size Limit
Process any amount of text — everything runs in your browser with no upload limits.
100% Private
Your data never leaves your browser. No server-side processing, no logging.
FAQ
What is Base64 encoding?
Base64 is a binary-to-text encoding scheme that converts binary data into ASCII characters. It's commonly used in email attachments, data URIs, API authentication tokens, and embedding binary data in text formats like JSON or XML.
Is Base64 encryption?
No. Base64 is encoding, not encryption. It doesn't provide any security — anyone can decode a Base64 string. It's used for data transport, not data protection.
What is URL-safe Base64?
Standard Base64 uses + and / characters which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _ to make the encoded string safe for use in URLs and filenames.
Why does Base64 increase size?
Base64 encodes 3 bytes into 4 characters, resulting in approximately 33% size increase. This is the tradeoff for being able to represent binary data as text.
Understanding Base64 Encoding: What It Is and How It Works
Base64 is a binary-to-text encoding scheme that converts binary data (such as files, images, or byte streams) into a sequence of 64 printable ASCII characters. This character set consists of uppercase letters A-Z, lowercase letters a-z, numbers 0-9, and the characters "+" and "/". The equals sign (=) is appended at the end as padding when the size of the binary input is not divisible by three bytes.
The primary purpose of Base64 is to transmit binary data over media that are designed to handle only text data. Many legacy communication protocols, such as SMTP email headers or JSON API endpoints, are structured exclusively around text characters. If you attempt to send raw binary data through these systems, the data can be modified or corrupted. By encoding it to Base64, you guarantee the data remains intact during transit.
It is important to remember that Base64 is not encryption. Encoding is a public, standard algorithm (defined in RFC 4648) and can be easily reversed in a split second by anyone using a basic decoder. Never use Base64 to secure passwords, credentials, or sensitive user information.
Common Use Cases in Modern Web Development
Inline Data URIs: Developers frequently embed small assets (like SVG icons, PNG badges, or web fonts) directly inside HTML or CSS files using Base64-encoded strings (e.g., data:image/png;base64,...). This eliminates the need for separate HTTP requests, resulting in faster rendering times for small resources.
API Communication: When posting files or binary keys via REST APIs that accept only JSON request bodies, Base64 is the industry standard format. The binary file is converted to a string and safely embedded within the JSON properties.
Basic Authentication: HTTP Basic access authentication uses Base64 to encode the username and password pair before sending it in the request's Authorization header (e.g., Authorization: Basic YWRtaW46cGFzc3dvcmQ=). Note that this is only secure when wrapped inside an encrypted HTTPS connection.
CI/CD Variables: Many build systems and environment configuration setups restrict special characters. Base64 is used to encode certificates, keys, or complex configurations to prevent shell interpretation issues during builds.
Standard Base64 vs. URL-Safe Base64
Standard Base64 encoding utilizes the "+" and "/" characters, which carry specific semantic meanings in URLs (representing spaces and path separators respectively). If you pass a standard Base64 string inside a URL query parameter, it will often break or require percentage encoding.
To solve this, URL-Safe Base64 (or Base64url) replaces "+" with "-" and "/" with "_", and typically strips the trailing padding "=" characters. This makes the string safe to pass in query parameters, path variables, or headers. Our tool supports both standards: toggle the "URL-safe" checkbox to instantly change the format.
Base64 Encoding FAQ
Why does Base64 increase file size?
Base64 works by grouping binary data into 6-bit chunks, representing each chunk as a single ASCII character. Since 8 bits make up a standard byte, this conversion results in a size overhead of approximately 33%. For instance, a 75KB binary image will compile into a 100KB Base64 text string.
How does browser-side decoding work?
This utility executes entirely client-side using standard Web APIs like btoa() and atob(). Since all computations are processed locally inside your web browser, no raw text or binary data is sent over the internet to CyberScryb servers. Your data remains fully private.
What does the trailing '=' padding character mean?
Base64 requires the input bits to align perfectly in 24-bit blocks (which maps to 4 characters of output). If your input ends and leaves remaining bytes, padding characters (=) are appended to complete the block. One "=" indicates there was one remaining byte; "==" indicates two remaining bytes.