Question 1

how to decode base64 to text

Accepted Answer

Paste the string and switch to decoding. Both the standard alphabet and the base64url variant are accepted — the one where `+` and `/` are written as `-` and `_` — and missing padding is added for you. Whitespace and line breaks inside the string are ignored, so pasting straight out of an email or a config file works.

Question 2

why is base64 33 percent larger

Accepted Answer

Because three bytes of input are written as four printable characters, so the output is four thirds of the input, plus whatever line breaks you add. That overhead buys the ability to send binary data through a channel that only accepts text, which is why email attachments and data URIs have used it for decades.

Question 3

is base64 encryption

Accepted Answer

No. Base64 is an encoding: there is no key and no secret involved. Anyone holding the string recovers the original data in a second with this very page. Storing passwords, tokens or personal data in Base64 and treating that as protection is a common and expensive mistake — it hides nothing from anyone.

Question 4

what is the difference between base64 and base64url

Accepted Answer

Two characters and the padding. Standard Base64 uses `+` and `/`, which have their own meaning inside URLs and file names, so the URL-safe variant writes them as `-` and `_` and usually drops the trailing `=`. JWTs, for instance, are base64url — which is why pasting one into a strict decoder fails.

Question 5

why does my base64 string end with equals signs

Accepted Answer

That is padding. Encoding works on blocks of three bytes, and when the final block holds one or two bytes the remaining space is marked with `=`. So a well-formed string has a length divisible by four and never more than two equals signs at the end — three or more means the string is damaged.

Question 6

does the data leave my browser

Accepted Answer

No. Both encoding and decoding happen locally and the contents of the field are never uploaded. It matters here more than on most pages: Base64 is the usual wrapper for exactly the things you should not paste elsewhere — private keys, certificates, mail attachments. Only the name of the opened tool is sent.

Base64

Encoder

How it works

About Base64

Standard Base64

URL-safe Base64

Character encoding

Where it's used

Frequently asked questions

how to decode base64 to text

why is base64 33 percent larger

is base64 encryption

what is the difference between base64 and base64url

why does my base64 string end with equals signs

does the data leave my browser

Base64

Encoder

How it works

About Base64

Standard Base64

URL-safe Base64

Character encoding

Where it's used

Frequently asked questions

how to decode base64 to text

why is base64 33 percent larger

is base64 encryption

what is the difference between base64 and base64url

why does my base64 string end with equals signs

does the data leave my browser

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