Question 1

Is Base64 encryption?

Accepted Answer

No. Base64 is an encoding, not encryption - anyone can decode it instantly with no key or password required, this tool included. It only changes the representation of data so it can safely pass through systems that expect text, not binary. Never use it to hide anything sensitive.

Question 2

Why does Base64-encoded text end with = signs?

Accepted Answer

Base64 works in 3-byte chunks, each turned into 4 output characters. When the input isn't a multiple of 3 bytes, = characters pad the last chunk out to a full 4 characters. The URL-safe variant typically drops this padding since decoders can usually infer it from the string's length.

Question 3

What's the difference between the standard and URL-safe alphabets?

Accepted Answer

Standard Base64 uses + and / as two of its 64 characters, but both have special meaning inside a URL (space and path separator, respectively), so a standard Base64 string can break when placed directly in a URL or filename. The URL-safe variant substitutes - and _ for those two characters instead, which is why it's the format used inside JWTs and similar tokens.

Question 4

Why does decoding sometimes show binary data instead of text?

Accepted Answer

Base64 can encode literally any bytes, not just text - an image, a font file, an executable. When the decoded bytes don't form valid UTF-8 text, this tool can't display them as a readable string, but you can still download them as a file to recover the original binary content.

Question 5

Why is Base64-encoded output around a third bigger than the original?

Accepted Answer

Base64 maps every 3 input bytes to 4 output characters, so the encoded result is always about 4/3 (roughly 33%) larger than the source, whether you're encoding a snippet of text or a whole file. That overhead is the price of representing arbitrary binary data with only 64 printable characters - it's normal and doesn't mean anything went wrong.

Question 6

Do I need to turn on 'URL-safe alphabet' before decoding a URL-safe Base64 string?

Accepted Answer

No - decoding always works whether the string uses the standard alphabet or the URL-safe one. Behind the scenes, this tool converts - and _ back to + and /, and restores any missing = padding automatically, so you can paste either variant straight into decode mode. The checkbox only matters for encoding, since it controls which alphabet the output uses.

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Base64 & URL Encoder

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