How much larger is Base64 than the original data?

Base64 encoding increases data size by approximately 33%. Every 3 bytes of input become 4 bytes of Base64 output. For example, a 1 MB file becomes approximately 1.33 MB when Base64 encoded.

Where is Base64 encoding commonly used?

Base64 is used in email attachments (MIME), data URIs for embedding images in HTML/CSS, API authentication (Basic Auth), JSON Web Tokens (JWT), and storing binary data in JSON or XML.

Base64 Encoder & Decoder

Encode and decode Base64 strings in real-time. Supports text input, file uploads, and URL-safe encoding. 100% client-side — your data never leaves your browser.

URL-safe modeUpload File

Text Input0 chars

Base64 Output0 chars

What is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that converts binary data into a sequence of 64 printable ASCII characters. It was originally designed to safely transmit binary data over text-based protocols like SMTP (email) and HTTP.

The encoding uses the characters A-Z, a-z, 0-9, + and / (with = for padding). Every 3 bytes of input data are converted into 4 Base64 characters, resulting in a ~33% size increase.

Common Base64 Use Cases

Base64 encoding is used throughout web development and system administration for safe data transmission.

Data URIs

Embed small images directly in HTML and CSS using data:image/png;base64,... format, eliminating extra HTTP requests.

API Authentication

HTTP Basic Auth encodes username:password in Base64 for the Authorization header.

Email Attachments

MIME encoding uses Base64 to safely transmit binary files through email (SMTP) protocols.

JWT Tokens

JSON Web Tokens encode the header and payload as Base64url strings for safe URL transmission.

Developer Tools & API Platforms (2026)

Building APIs that use Base64? These platforms make API development, testing, and monitoring easier.

Tool	Type	Price	Key Features	Link
Postman Recommended	API Platform	Free / $14/mo	API testing, Base64 encoding, team collaboration	Visit
Insomnia Open source	REST Client	Free / $5/mo	REST/GraphQL client, env variables, plugins	Visit
Hoppscotch Browser-based	API Client	Free	Open source, real-time, WebSocket support	Visit
RapidAPI API Marketplace	Hub + Testing	Free / $20/mo	API marketplace, testing, monitoring, analytics	Visit

Frequently Asked Questions

What is Base64 encoding?

Base64 is a binary-to-text encoding scheme that converts binary data into ASCII characters using 64 printable characters (A-Z, a-z, 0-9, +, /). It's commonly used to transmit binary data over text-based protocols like email, HTTP, and JSON.

Is Base64 encoding the same as encryption?

No. Base64 is an encoding format, not encryption. It provides no security whatsoever — anyone can decode a Base64 string. It's designed for data format conversion, not confidentiality. For actual security, use encryption like AES-256.

What is URL-safe Base64?

URL-safe Base64 (also called Base64url) replaces + with -, / with _, and omits = padding characters. This makes the output safe for URLs, filenames, and query parameters without requiring percent-encoding. It's used in JWT tokens and many APIs.

How much larger does Base64 make data?

Base64 encoding increases data size by approximately 33%. Every 3 bytes of input become 4 characters of output. A 1 MB file becomes ~1.33 MB when Base64 encoded. This overhead is why Base64 is best for small to medium data, not large files.

Can I Base64 encode binary files like images?

Yes. Base64 can encode any binary data including images, PDFs, and executables. This is commonly used for data URIs (embedding images in HTML/CSS) and sending files via JSON APIs. Use the file upload feature above to encode files.

Is my data safe using this tool?

Yes. This tool runs entirely in your browser using JavaScript's built-in btoa() and atob() functions. No data is sent to our servers. You can verify this by checking your browser's Network tab — no requests are made when encoding or decoding.

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