Base64 is a way to represent binary data or text as a string of safe ASCII characters, so it can travel through systems that only handle plain text. The tool below encodes any text to Base64 or decodes Base64 back to the original, working entirely in your browser. Base64 is encoding, not encryption: anyone can decode it.
What Base64 Is and What It Is For
Base64 is an encoding scheme that converts arbitrary bytes into a limited set of 64 characters that every system treats as plain text: the letters A to Z and a to z, the digits 0 to 9, and the two symbols + and /. The problem it solves is transport. Many channels were built for text and can corrupt or reject raw binary data, such as an image, a file, or bytes outside the printable range. Encoding that data as Base64 turns it into a string those channels carry safely, and decoding on the other side rebuilds the exact original bytes.
How to Use This Base64 Tool
- Choose a mode. Pick Encode to Base64 to turn text into Base64, or Decode from Base64 to turn Base64 back into text.
- Type or paste your input into the box. The tool reads it as you type.
- Read the result below the box. It updates automatically, or press Convert to run it again.
- Press Copy to put the result on your clipboard.
- If you decode and see Not valid Base64, the input is not a complete, correctly padded Base64 string.
How Base64 Works: 3 Bytes to 4 Characters
Base64 works in groups of 3 bytes. Three bytes are 24 bits, and Base64 splits those 24 bits into four groups of 6 bits. Each 6 bit group is a number from 0 to 63, which maps to one character in the 64 character alphabet. So every 3 bytes of input become exactly 4 output characters, which is why Base64 output is about one third larger than the original data. When the input does not divide evenly into groups of 3, the encoder pads the final group with one or two = characters to mark how many bytes were missing, so the decoder can rebuild the original length exactly.
Where Base64 Is Used
Small images and fonts get embedded directly in HTML or CSS as a data: URI, with the file bytes written inline as Base64 so the browser needs no extra request.
The MIME standard encodes attached files as Base64 so binary content survives mail servers that were designed for text only.
JSON Web Tokens, API keys, and certificates are often Base64 so they fit on one line in headers, URLs, and config files. The payload is readable, not secret.
Is It Private? Yes, It Runs in Your Browser
Everything this tool does happens on your own device. The encoding and decoding run in your browser with the built in btoa and atob functions, and your input is never uploaded, logged, or stored on any server. You can confirm this by disconnecting from the internet and watching the tool still work. That makes it safe to use even with text you would not want to send to a third party, though remember that Base64 itself adds no protection once the string leaves your hands.
Related Tools
Encode text for safe use inside web addresses and query strings.
Format and validate JSON, including payloads that carry Base64 fields.
Produce a one way hash of text, which unlike Base64 cannot be reversed.
Last Thoughts on Base64 Encoding
Base64 is one of the quiet workhorses of computing. It does one job well: it turns any bytes into safe text so they can pass through channels that only understand text, then turns them back without losing a single bit. The cost is a string about a third larger than the original, which is a fair price for guaranteed safe transport.
The one rule to keep in mind is that Base64 protects nothing, because anyone can decode it. Use it to move data, and reach for real encryption when you need to keep data secret. To see how characters become the bytes that Base64 carries, read our explainer on ASCII vs Unicode, and explore the rest of our free online tools.
Key Takeaways:
- Base64 represents binary data or text as 64 safe ASCII characters so it can travel through text only channels.
- It encodes every 3 bytes as 4 characters, padding the end with = when the input does not divide evenly.
- Base64 output is about one third larger than the original data.
- Base64 is encoding, not encryption: anyone can decode it, so never use it to protect secrets.
- Common uses are data URIs, email attachments, and tokens such as JSON Web Tokens.
- This tool runs entirely in your browser; nothing you enter is uploaded.
Frequently Asked Questions (FAQs)
Is Base64 a form of encryption?
No. Base64 is encoding, not encryption. It uses no key and keeps no secret, so anyone who sees a Base64 string can decode it back to the original in seconds. It makes data safe to transport, not safe from being read. When you need to keep data secret you need real encryption instead.
Why is Base64 output larger than the input?
Because Base64 turns every 3 bytes of data into 4 characters, the output is about one third larger than the original. Each output character also carries only 6 bits of real data inside an 8 bit character. The size increase is the trade for being able to move the data safely through text only channels.
What do the = signs at the end of Base64 mean?
The = characters are padding. Base64 works in groups of 3 bytes, and when the final group has only 1 or 2 bytes, the encoder adds 1 or 2 = signs to mark how many bytes were missing. The decoder reads the padding to rebuild the original length exactly. A correctly formed Base64 string is always a multiple of 4 characters long.
Why do I get a Not valid Base64 error when decoding?
That message means the input is not a complete, correctly formed Base64 string. Common causes are missing padding, stray spaces or line breaks, or characters that are not part of the Base64 alphabet. Check that you pasted the full string and nothing extra, then try again. The tool only decodes input that is genuinely valid Base64.
Does this tool send my text to a server?
No. The encoding and decoding run entirely inside your browser using its built in functions, and your input is never uploaded, logged, or stored anywhere. You can confirm this by disconnecting from the internet and watching the tool still work. It is safe to use even with text you would not want to send elsewhere.
Can Base64 encode any kind of data?
Yes. Base64 can encode any bytes, including text, images, audio, and other files, because it operates on the raw bytes rather than on the meaning of the data. This tool focuses on text and handles the full UTF-8 range correctly, so letters and symbols from any language encode and decode without loss.
