Base64 Encoder/Decoder

What is the Base64 Encoder/Decoder?

Base64 is an encoding that represents arbitrary bytes using only 64 printable ASCII characters: A-Z, a-z, 0-9, + and /, with = used for padding. It exists because many protocols, such as email (MIME), JSON and HTTP headers, were designed for text and cannot safely carry raw binary data.

Base64 is not encryption. Anyone can decode it, so it must never be used to protect secrets. It also increases size by roughly one third, because every 3 bytes of input become 4 characters of output. The URL-safe variant replaces + and / with - and _ so the result can be used in URLs and JWTs without escaping.

When to use the Base64 Encoder/Decoder

Developers use Base64 to embed small images in CSS or HTML as data URIs, to carry binary attachments inside JSON, to read the credentials in an HTTP Basic authentication header, and to inspect the segments of a JWT. Mail systems encode attachments with it, and many APIs return signatures or keys in Base64. When something looks like a long string of letters and digits ending in equals signs, decoding it is often the quickest way to learn what it contains, whether that turns out to be readable text, JSON or binary data such as an image.

How to use the Base64 Encoder/Decoder

1. Choose Encode or Decode.
2. Paste your text or Base64 string into the input box.
3. Enable the URL-safe option if the string will be used in a URL, filename or JWT segment.
4. The output updates immediately; invalid Base64 shows a clear error.
5. Copy the result with one click.

Examples

Text:    Hello, World!
Base64:  SGVsbG8sIFdvcmxkIQ==

Text:    héllo ✓
Base64:  aMOpbGxvIOKckw==

URL-safe (no padding):  SGVsbG8sIFdvcmxkIQ

In JavaScript, btoa() only handles Latin-1, so UTF-8 text must be converted to bytes first, which this tool does for you.

Common errors and tips

• Incorrect padding errors appear when the string length is not a multiple of 4; add = characters or enable padding repair.
• Whitespace and line breaks copied from emails are ignored by the decoder, but other characters are not.
• Decoded output that looks like random symbols usually means the original data was binary (an image or archive), not text.
• Never treat Base64 as a way to hide passwords or API keys.
• Use the URL-safe alphabet for JWT segments and query string values.

Privacy: runs entirely in your browser

Encoding and decoding use your browser's built-in functions; the text you enter is never sent over the network. This tool runs entirely in your browser: nothing you enter is uploaded, stored or logged on our servers, and it keeps working even if you go offline after the page has loaded.