How do I decode a Base64 string to text?

Choose Decode and paste the string. SGVsbG8= and SGVsbG8 both decode to Hello, because padding is optional, and spaces or line breaks in the pasted text are ignored. A string in the URL-safe alphabet decodes too: aGVsbG8_Pj4 gives hello?>>.

Why does decoding say the Base64 is binary data, not UTF-8 text?

The string is valid Base64, but the bytes it holds are not UTF-8 text. /w== is the single byte 0xFF, which UTF-8 never uses, so the page reports binary data instead of an invalid string. Use Base64 File to String to decode it to a file.

What is URL-safe Base64?

It is the same encoding with - and _ in place of + and /, usually without the = padding, so the text can sit in a URL or a file name (RFC 4648, section 5). hello?>> is aGVsbG8/Pj4= in the standard form and aGVsbG8_Pj4 in the URL-safe form. A string that mixes + or / with - or _ is rejected as invalid.

Why does Base64 end with = or ==?

Base64 reads 3 bytes at a time and writes 4 characters. When the input is 1 byte over a multiple of 3, two = pad the end (a gives YQ==), and when it is 2 bytes over, one = does (ab gives YWI=). A multiple of 3 bytes, such as abc giving YWJj, needs none.

Is Base64 encryption?

No. It is a reversible encoding that anyone can decode, as dXNlcjpwYXNz decoding to user:pass shows. Do not use it to hide a password or a key.

Is there a size limit, and is my text uploaded?

Input is limited to 250,000 characters, and a longer paste shows a message instead of a result. The conversion runs in your browser and the text is not uploaded.

Base64 Converter

Encode text to Base64 or decode Base64 to text. UTF-8, standard and URL-safe alphabets, optional padding on decode, up to 250,000 characters. How it works

Text to Encode

Result

About the Base64 Converter

Hello in Base64 is SGVsbG8=. The converter turns text into UTF-8 bytes, writes every 3 bytes as 4 characters and pads the end with = when the last group is short. Decoding reverses it and accepts both the standard and the URL-safe alphabet. It handles text only, so use Base64 File to String for a file.

Text, its UTF-8 size and its Base64 form

Text	UTF-8 bytes	Standard Base64	URL-safe Base64
a	1	YQ==	YQ
ab	2	YWI=	YWI
abc	3	YWJj	YWJj
Hello	5	SGVsbG8=	SGVsbG8
Hello, World!	13	SGVsbG8sIFdvcmxkIQ==	SGVsbG8sIFdvcmxkIQ
user:pass	9	dXNlcjpwYXNz	dXNlcjpwYXNz
é	2	w6k=	w6k
日本	6	5pel5pys	5pel5pys
hello?>>	8	aGVsbG8/Pj4=	aGVsbG8_Pj4

Each row is what the converter returns, with and without the URL-safe option. The URL-safe form swaps + and / for - and _ and drops the = padding (RFC 4648, section 5). A multiple of 3 bytes needs no padding.

How to use this tool

Choose Encode to turn text into Base64, or Decode to turn Base64 into text.
Type or paste the input. The result appears as you type.
In Encode mode, switch on URL-safe output for - and _ with no padding.
Press Copy to copy the result.

Frequently asked questions

How do I decode a Base64 string to text?: Choose Decode and paste the string. SGVsbG8= and SGVsbG8 both decode to Hello, because padding is optional, and spaces or line breaks in the pasted text are ignored. A string in the URL-safe alphabet decodes too: aGVsbG8_Pj4 gives hello?>>.
Why does decoding say the Base64 is binary data, not UTF-8 text?: The string is valid Base64, but the bytes it holds are not UTF-8 text. /w== is the single byte 0xFF, which UTF-8 never uses, so the page reports binary data instead of an invalid string. Use Base64 File to String to decode it to a file.
What is URL-safe Base64?: It is the same encoding with - and _ in place of + and /, usually without the = padding, so the text can sit in a URL or a file name (RFC 4648, section 5). hello?>> is aGVsbG8/Pj4= in the standard form and aGVsbG8_Pj4 in the URL-safe form. A string that mixes + or / with - or _ is rejected as invalid.
Why does Base64 end with = or ==?: Base64 reads 3 bytes at a time and writes 4 characters. When the input is 1 byte over a multiple of 3, two = pad the end (a gives YQ==), and when it is 2 bytes over, one = does (ab gives YWI=). A multiple of 3 bytes, such as abc giving YWJj, needs none.
Is Base64 encryption?: No. It is a reversible encoding that anyone can decode, as dXNlcjpwYXNz decoding to user:pass shows. Do not use it to hide a password or a key.
Is there a size limit, and is my text uploaded?: Input is limited to 250,000 characters, and a longer paste shows a message instead of a result. The conversion runs in your browser and the text is not uploaded.

Reading Basic auth values, JSON fields and URL-safe tokens

Read or write the text side of web plumbing: a Basic authorization value such as dXNlcjpwYXNz, which decodes to user:pass, a Base64 field in a JSON payload or a config file, or a token fragment written in the URL-safe alphabet. Choose Encode or Decode, then paste or type; the result updates as you type. The conversion runs in your browser and the text is not uploaded.

A decode that fails usually means the string was cut short, picked up a stray character such as a quote or a comma when it was copied, or mixes the two alphabets. For a file or an image use Base64 File to String instead, because this page handles text only.

How the encoding works

The text is first turned into UTF-8 bytes, so é is 2 bytes and 日 is 3. Base64 then reads the bytes 3 at a time (24 bits) and writes each group as 4 characters from a 64-character alphabet: A-Z a-z 0-9 + /. If the last group is short, = pads the output to a multiple of 4 (RFC 4648, section 4).

Example: Hello is 5 bytes and encodes to SGVsbG8=. 日本 is 6 bytes and encodes to 5pel5pys.

The URL-safe option uses the alphabet from section 5 of the same RFC: - and _ replace + and /, and the padding is dropped. hello?>> is aGVsbG8/Pj4= in the standard form and aGVsbG8_Pj4 in the URL-safe form.

Decoding accepts either alphabet but not both in one string, ignores spaces and line breaks, and does not need the padding. The decoded bytes must be valid UTF-8 text. If they are not, as with the single byte in /w==, the page says the Base64 decodes to binary data instead of calling it invalid. Input is limited to 250,000 characters.

Fun Fact: Every 3 bytes become 4 characters, so Base64 text is about one third longer than the data it encodes: the 5 bytes of Hello become 8 characters (RFC 4648, section 4).

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