Question 1

Can it decode a JWT segment or other base64url string?

Accepted Answer

Yes. The URL-safe alphabet uses - and _ where standard Base64 uses + and /, and usually drops the = padding. Both are accepted on decode without a setting to flip, and the padding is restored for you. Tick URL-safe when encoding to produce that variant.

Question 2

How do I turn an image into a data URI?

Accepted Answer

Drop the file on the input while Encode is selected. You get back data:image/png;base64,… ready to paste into a CSS background or an <img> tag, and untick the prefix option if you only want the raw Base64. Files up to 2 MB work.

Question 3

I decoded something and got a download button instead of text. Why?

Accepted Answer

Because the bytes aren't text. Base64 carries any data, so decoding an image or a PDF would otherwise fill the box with unreadable characters. When the result isn't valid UTF-8, you get the file instead, named from the data URI's type when there is one.

Question 4

Does it handle special characters and emoji correctly?

Accepted Answer

Yes, text is UTF-8 encoded before conversion, so accented letters, emoji, and non-Latin scripts round-trip correctly.

Question 5

What happens if I try to decode invalid Base64?

Accepted Answer

You get the specific character and its position, for example '"!" at position 6 isn't a Base64 character', rather than a blanket "invalid input". Line breaks and spaces are ignored, so text copied out of a PEM file or an email header decodes as it is.

Question 6

Is Base64 the same as encryption?

Accepted Answer

No, Base64 is just a reversible encoding format, not encryption. Anyone can decode it back to the original text; it provides no security or privacy.

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Base64 Encoder/Decoder

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