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Base64 Encoder / Decoder

Encode text to Base64 or decode Base64 strings instantly. Supports UTF-8 and file encoding.

Mode

Text to Encode

0 characters

Or Upload a File

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What Is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that represents binary data using a set of 64 ASCII characters (A-Z, a-z, 0-9, +, /). It is designed to carry data stored in binary formats across channels that only reliably support text content.

How Base64 Works

Base64 encoding takes every three bytes (24 bits) of input and splits them into four 6-bit groups. Each 6-bit value maps to one of the 64 characters in the Base64 alphabet. If the input length is not a multiple of three, padding characters (=) are added to the output.

Common Uses of Base64

Data URIs: Embedding images, fonts, or other assets directly in CSS or HTML using data:image/png;base64,... eliminates extra HTTP requests.
Email (MIME): Email protocols like SMTP are text-based, so binary attachments (images, PDFs) are Base64-encoded before transmission.
API Authentication: HTTP Basic Authentication encodes username:password in Base64 before sending it in the Authorization header.
JSON Payloads: When binary data needs to travel inside a JSON object (which only supports text), Base64 is the standard encoding.
JWT Tokens: JSON Web Tokens encode their header and payload sections using Base64URL (a URL-safe variant).

Base64 and File Size

Base64 encoding increases data size by approximately 33% because three bytes of input become four bytes of output. This trade-off is acceptable for small assets but can be costly for large files. For images above a few kilobytes, serving them as separate files with proper caching is usually more efficient than inlining as Base64.

Unicode Support

The browser-native btoa() function only handles Latin-1 characters. To encode Unicode text (emojis, CJK characters, etc.), the input must first pass through TextEncoder to produce UTF-8 bytes, which are then Base64-encoded. This tool handles Unicode automatically.

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How to Use the Base64 Encoder / Decoder

1
Enter your values
Open the Base64 Encoder / Decoder and fill in the required input fields with your numbers or selections.
2
Review the calculation
The tool automatically computes the result as you type. Double-check your inputs to ensure accuracy.
3
Interpret your results
Review the calculated output along with any breakdowns, charts, or explanations provided to understand what the numbers mean for your situation.

Sources & Verification

MDN Web Docs ECMAScript Language Specification

Published by ConvertCrunch Editorial Team | Our Methodology

Frequently Asked Questions

What is the Base64 Encoder / Decoder?

The Base64 Encoder / Decoder is a free browser-based tool on ConvertCrunch. Encode text to Base64 or decode Base64 strings instantly. Supports UTF-8 and file encoding. It requires no downloads, installations, or account signups. Simply enter your values and get instant, accurate results. The tool is designed for quick calculations and informed decision-making, whether you are a professional, student, or everyday user looking for reliable answers.

How do I use the Base64 Encoder / Decoder?

Using the Base64 Encoder / Decoder is straightforward. Enter your values into the input fields provided on the page, then calculate or adjust parameters to explore scenarios. Most processing happens locally in your browser. If a feature uses a third-party service, the tool identifies that connection and the privacy policy explains it. Most users get the answers they need in under a minute.

Is the Base64 Encoder / Decoder free to use?

Yes, the Base64 Encoder / Decoder is completely free to use with no account signup, email requirement, or premium tier. Most calculations run locally in your browser. Features that depend on live data or a third-party service require a network connection and are identified in the tool. You can use it as many times as you need for personal, educational, or professional purposes.

How accurate is the Base64 Encoder / Decoder?

The Base64 Encoder / Decoder uses standard algorithms, encoding specifications, and well-tested implementations. Output is deterministic and verifiable against official specifications. For encoding, hashing, and conversion tools, results match the relevant RFC or standard exactly. For estimation tools, results are based on industry benchmarks and may vary based on your specific environment and configuration.

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What Is Base64 Encoding?

How Base64 Works

Common Uses of Base64

Data URIs: Embedding images, fonts, or other assets directly in CSS or HTML using data:image/png;base64,... eliminates extra HTTP requests.
Email (MIME): Email protocols like SMTP are text-based, so binary attachments (images, PDFs) are Base64-encoded before transmission.
API Authentication: HTTP Basic Authentication encodes username:password in Base64 before sending it in the Authorization header.
JSON Payloads: When binary data needs to travel inside a JSON object (which only supports text), Base64 is the standard encoding.
JWT Tokens: JSON Web Tokens encode their header and payload sections using Base64URL (a URL-safe variant).