How the Base64 Encoder / Decoder works

Choose Encode to turn text into Base64, or Decode to turn Base64 back into text. Text is converted to and from UTF-8 bytes and standard Base64 locally in your browser — nothing is uploaded to a server or sent to PocketSpry’s AI API. Encoding produces canonical Base64 with standard `=` padding; decoding ignores line breaks and spaces so wrapped Base64 still works.

Base64 and UTF-8

Base64 represents bytes, not characters. To encode text this tool first converts it to UTF-8 bytes, then Base64-encodes those bytes, so accented characters, emoji, and non-English text all round-trip correctly. When decoding, it requires the decoded bytes to be valid UTF-8 text: if they are not, it reports an error instead of silently inserting replacement characters. That is also why encoding plain text with a raw byte-oriented function like btoa fails on Unicode — it treats each character as a single byte.

Standard Base64 vs Base64URL

This tool uses the standard Base64 alphabet: A–Z, a–z, 0–9, plus + and /, with = padding. It does not silently interpret the Base64URL variant, which uses - and _ instead of + and /. If your input contains - or _, the decoder reports that it is Base64URL rather than guessing, because those characters decode to different bytes.

Is Base64 encryption?

No. Base64 is an encoding, not encryption or security. It is fully reversible with no key — anyone who has a Base64 value can decode it back to the original text. Do not use Base64 to hide, protect, or secure sensitive data.

Frequently asked questions

What is Base64?: Base64 is a way to represent binary data (here, the UTF-8 bytes of your text) using 64 printable ASCII characters. It is commonly used to embed or transmit data through text-only channels.
Is Base64 encryption?: No. Base64 is a reversible encoding with no key or secret. Anyone with the encoded value can decode it, so it does not protect or secure data.
What text encoding does this use?: UTF-8. Text is encoded to UTF-8 bytes before Base64, and decoded bytes must be valid UTF-8.
Can it encode emoji and non-English text?: Yes. Because it uses UTF-8, accented characters, emoji, and CJK or other scripts all work.
Why does btoa sometimes fail on Unicode?: The browser’s btoa expects a byte-oriented string and treats each character as a single byte, so it throws or corrupts characters above the basic Latin range. This tool converts text to UTF-8 bytes first, which handles all Unicode correctly.
Does the decoder accept line breaks?: Yes. ASCII whitespace such as spaces, tabs, and line breaks in the Base64 input is ignored.
Does it accept Base64 without = padding?: Yes, when the omitted trailing padding is structurally valid. Encoded output always includes standard = padding.
Does it support Base64URL?: No. It uses the standard + and / alphabet and does not auto-convert the Base64URL - and _.
Does it decode binary files?: No. Version 1 decodes Base64 that represents valid UTF-8 text, not arbitrary binary files.
What happens if decoded bytes are invalid UTF-8?: The tool returns an error rather than silently replacing the bytes, because it promises to decode Base64 that represents UTF-8 text.
Does PocketSpry upload my text?: No. Encoding and decoding run entirely in your browser.
Can I encode secrets with this?: Base64 does not encrypt or protect data; anyone who has the encoded value can decode it. Use proper encryption for anything sensitive.