Base64 Encoder / Decoder

What Base64 is (and isn't)

Base64 turns any bytes, text, images or files, into a string of 64 safe characters: A–Z, a–z, 0–9, + and /, with = as padding. It exists so binary data can travel through systems built for text: email, JSON, URLs, HTML, HTTP headers.

It is not encryption. Anyone can decode Base64 instantly; there's no key. If you see a password or API key "protected" with Base64, it isn't protected.

How much bigger Base64 makes your data

Every 3 bytes become 4 characters, so encoded data is about 33% larger:

That's why embedding large images as Base64 data URLs slows pages down: they're a third bigger than the file and can't be cached separately.

Padding: the = at the end

Base64 works in groups of 3 bytes. When the input doesn't divide evenly, = fills the gap:

Some systems (JWTs, many URL-based tokens) drop the padding. The decoder accepts Base64 with or without it.

Base64 vs Base64URL

Standard Base64 uses + and /, which have special meanings in URLs and file names. Base64URL swaps them for - and _:

Use Base64URL for anything that goes in a URL, a filename or a JWT. Use standard Base64 for email attachments, data URLs and most APIs. If a decoder rejects your string with "invalid characters", check whether it contains - or _ (it's Base64URL) or + and / (it's standard).

The accented-text bug in JavaScript

The browser's built-in btoa() only understands Latin-1 characters, and handles anything else badly:

So btoa("São Paulo") doesn't fail; it returns a string that other systems decode as garbage. This tool always encodes text as UTF-8, which is what every other language and API expects. In your own code, encode with TextEncoder first, or in Node.js use Buffer.from(text).toString("base64").

Data URLs

A data URL puts a whole file inside a string:

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA...

You can paste a full data URL into the decoder; it recognizes the prefix and gives you the file back to download with the right type. Data URLs are handy for small icons in CSS or email templates. For anything larger than a few kilobytes, a normal file is faster.

FAQ

Is my data sent to a server?

No. Encoding and decoding happen in your browser, including files. Nothing is uploaded to Docspira.

Can I encode a file, like an image or a PDF?

Yes. Choose a file and the tool gives you its Base64 text, or decode Base64 back into a downloadable file. The bytes are preserved exactly.

Why does my decoded text look like random symbols?

Either the Base64 represents binary data (an image, a zip file, compressed or encrypted data), not text, or the text was encoded with a different character set. Try downloading the decoded result as a file instead of reading it as text.

What does "invalid padding" mean?

The number of = characters at the end doesn't match the length of the data. That usually means the string was cut off when it was copied.

Can Base64 contain line breaks?

Email (MIME) wraps Base64 at 76 characters per line. The decoder accepts line-wrapped input and ignores the breaks.