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Base64 encoder and decoder that handles UTF-8 and binary properly

Base64 is easy to get subtly wrong: standard versus URL-safe alphabet, newline padding, and text that is not ASCII. This tool does the conversion correctly for all three and shows you exactly which variant it produced.

Alphabets
Standard + URL-safe
Encoding
UTF-8 aware
Binary
Supported
Base64 Encoder & Decoder Standard and URL-safe alphabets, UTF-8 aware
Result

How to use it

  1. Paste the value Type or paste the text to encode, or the Base64 string to decode. Decoding is detected automatically, so you do not need to switch modes first.
  2. Pick the variant Standard Base64 uses + and / and pads with =. URL-safe Base64 swaps them for - and _ and can drop the padding, which is what JWT and URL query parameters require.
  3. Copy the result The output shows the encoded string, its length before and after, and a ready-made data URI when the input looks like binary.

Reference

The same payload in both alphabets

InputStandardURL-safe
`{"a":1,"b":"x?y"}``eyJhIjoxLCJiIjoiePx5In0=``eyJhIjoxLCJiIjoiePx5In0=`
`binary bytes 0xFB 0xFF``+/8=``-_8=`

Questions people ask

Is Base64 encryption?

No. It is a reversible encoding with no key. Treat a base64-encoded value as plain text for confidentiality purposes, and encrypt anything that genuinely needs protecting.

What is the difference between standard and URL-safe Base64?

Standard Base64 uses + and / for the last two alphabet characters and pads with =. The URL-safe variant, defined in RFC 4648 section 5, replaces them with - and _ and usually drops the padding so the result can be placed in a URL without escaping.

Why did my Base64 decode to garbage?

Most often the string was encoded from binary rather than text and you are viewing it as a string. Second most common: the input is URL-safe Base64 that a strict standard decoder rejected — this decoder accepts both. Third: the string was truncated in transit, which you can spot in the length readout.

Does it handle emoji and non-Latin characters?

Yes. Text is converted to UTF-8 bytes before encoding, so emoji, accented letters, Cyrillic, Arabic and CJK text all round-trip correctly.

How large a file can I encode?

Text of a few megabytes is comfortable. For files, note that Base64 adds roughly a third in size, which is usually a bad trade compared with sending the file itself over HTTP.

Can I decode a Base64 image?

Yes, and the output includes the data URI form so you can paste it straight into an image tag or a stylesheet. The decoder also reports whether the decoded bytes look like a recognised image format.

Details that catch people out

Base64 is not encryption

Base64 is a transport encoding with no key and no confidentiality. Anyone can decode it, and a secret that is only base64-encoded is a secret that is public. It protects nothing against someone who can read the string.

Why padding matters

A standard Base64 string is padded with = to a multiple of four characters. URL-safe variants usually strip the padding. Decoders in strict mode will reject a string whose length and padding disagree, which is why the decoder here is tolerant and reports what it removed.

Where this earns its keep

Building a data URI for an inline image

The output includes the complete `data:image/png;base64,...` prefix, which is what you need to inline a small image in CSS or an email template.

Reading an encoded string from a config file

A base64 secret in a deployment manifest decodes in one step, so you can confirm what a value actually is without touching a terminal.

Preparing a JWT segment

JWTs use the URL-safe alphabet without padding, which is the single most common reason a hand-built token fails signature validation.

Guides that go deeper

Last reviewed 2026-10-10. Every tool on DevSnap runs entirely in your browser, so whatever you paste here never reaches a server.