Base64 Encode / Decode

Online Base64 Encoder and Decoder

Base64 is a binary-to-text encoding scheme that represents binary data as a string of printable ASCII characters. It works by taking every three bytes of input and splitting them into four groups of six bits, then mapping each group to one of 64 characters (A-Z, a-z, 0-9, +, and /). The result is a text string that can safely travel through systems designed to handle only text, such as email protocols, JSON payloads, and HTML attributes. This free tool lets you encode any text to Base64 or decode a Base64 string back to its original content, with full Unicode and UTF-8 support.

You will encounter Base64 constantly in modern development. Data URIs embed images directly in CSS or HTML to save HTTP requests. Email attachments are encoded with Base64 so they can travel through SMTP, which was designed for plain text. API authentication headers often carry Base64-encoded credentials. Understanding how to encode and decode Base64 is a practical skill that saves time during debugging, integration work, and everyday web development tasks.

How to Use This Base64 Tool

To encode plain text to Base64, type or paste your content into the input field and click the Encode button. The tool converts your text to its UTF-8 byte representation and then applies the Base64 encoding algorithm. The result appears instantly in the output field.

To decode a Base64 string, paste the encoded string into the input field and click Decode. The tool reverses the process, converting the Base64 characters back into the original bytes and then interpreting them as UTF-8 text. If the input is not valid Base64, you will see an error message indicating the problem.

Once you have your result, click the Copy button to send the output to your clipboard. This is useful when you need to paste a data URI into a stylesheet, drop an encoded token into an API request, or transfer decoded content into another tool. All processing happens in your browser, so nothing is sent to a remote server.

Key Features

Text-to-Base64 encoding. Converts any plain text string into its Base64-encoded equivalent. Useful for generating data URIs, preparing content for email transmission, or encoding credentials for HTTP Basic Authentication headers.

Base64-to-text decoding. Reverses the encoding process to recover the original text from a Base64 string. Helpful when you receive an encoded payload from an API, an email header, or a JWT token and need to inspect its contents.

Full UTF-8 and Unicode support. Unlike many Base64 tools that only handle basic ASCII, this encoder correctly processes multi-byte characters such as accented letters, CJK characters, and emoji. The tool encodes text to UTF-8 bytes before applying Base64, ensuring accurate round-trip conversion.

Instant output with copy to clipboard. Results appear as soon as you click Encode or Decode with no page reloads or loading spinners. The copy button places the output directly on your clipboard so you can paste it wherever it is needed.

Client-side processing. The encoding and decoding happen entirely in your browser. Your input data is never sent to a server, making it safe to use with API tokens, credentials, and other sensitive strings that should not be transmitted over the network.

When Not to Use Base64

Base64 is an encoding scheme, not a security measure. It should never be used to protect sensitive data because anyone can decode it trivially. If you need to secure data, use proper encryption algorithms instead. Additionally, Base64 increases the size of data by approximately 33 percent because it represents three bytes of input as four characters of output. This means that embedding large images as data URIs can actually make your page heavier than serving them as separate files. Use Base64 strategically for small assets, transport compatibility, and inline embedding where the convenience outweighs the size cost.

Frequently Asked Questions

Is Base64 the same as encryption?

No. Base64 is an encoding format, not an encryption method. Encoding transforms data into a different representation so it can be safely transmitted through text-based systems, but it does not protect the data in any way. Anyone with access to a Base64 string can decode it instantly without a key or password. If you need to protect sensitive information, use a proper encryption algorithm such as AES or RSA. Base64 is about compatibility and transport, not confidentiality.

Why does Base64 increase file size?

Base64 represents every three bytes of binary data as four ASCII characters. This means the output is always about one-third larger than the input. The overhead exists because Base64 uses only 64 printable characters from the much larger 256-value byte range, so more characters are needed to carry the same amount of information. When padding characters are added to align the output to a multiple of four, the increase can be slightly more. For small pieces of data like icons or short strings the overhead is negligible, but for large files it adds up quickly.

When should I use Base64 encoding?

Base64 is most useful when you need to embed binary data in a text-only context. Common use cases include embedding small images or fonts directly in CSS or HTML using data URIs, encoding file attachments for transmission over SMTP email, passing binary data inside JSON or XML payloads, and encoding credentials for HTTP Basic Authentication. It is also used internally by JWT tokens to encode the header and payload sections. As a rule of thumb, use Base64 when the receiving system expects text and you need to send something that is not pure text.

Can anyone decode my Base64 string?

Yes. Base64 decoding is a deterministic, reversible process that requires no secret key. Any Base64 decoder, including this tool, free online services, command-line utilities, and built-in programming language functions, can convert a Base64 string back to its original form. This is by design. Base64 was created for data transport, not secrecy. Never rely on Base64 to hide passwords, API keys, or other sensitive information. Always use encryption when confidentiality is required.