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Base64 Decoder

Decode a Base64 string back to text. Both the standard and URL-safe alphabets are accepted, so a JWT segment can be pasted straight in without converting it first.

Encoding is not encryption

Base64 makes data safe to transport, not secret. Anyone can decode it in one step. Never use it to protect passwords, tokens or personal data. Everything here runs in your browser and nothing is uploaded.

How to use this tool

  1. Paste the Base64 string.
  2. The decoded text appears below. Whitespace and line breaks in the input are ignored.

Notes and limitations

  • Both alphabets are accepted. URL-safe input using - and _ is converted automatically and missing padding is restored.
  • If the decoded bytes are not valid UTF-8, the tool says so rather than returning a string full of replacement characters. That usually means the data is a binary file — an image or a PDF — rather than text.
  • Decoding proves nothing about where the data came from. Base64 offers no integrity check, so decoded content can have been altered in transit.
  • Everything runs in your browser and nothing is uploaded. That said, treat any third-party website with caution when handling production data — if a value would cause real damage if leaked, process it with your own local tooling instead.

Frequently asked questions

Why does my Base64 fail to decode?

Usually the string is incomplete, or characters were lost when it was copied. Base64 contains only letters, digits and a few symbols; anything else means the string has been corrupted or is not Base64 at all.

Can I decode a JWT here?

You can decode an individual segment, since JWT segments are URL-safe Base64. The JWT Decoder is easier — it splits the token and labels the claims for you.

What if the result is unreadable?

The data is probably a binary file rather than text. Base64 is often used for images and attachments, which have no meaningful text representation.

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