Email & encoding
Free Base64 Decoder
Decode Base64 to readable text in your browser. Handles UTF-8, URL-safe Base64 and data URL prefixes, and tells you when the input is not valid.
Start with the example, or enter your own text.
How to use this tool
- Paste the Base64 string, with or without a data URL prefix.
- Decode it to see the original UTF-8 text.
- Copy the decoded text or download it.
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Open tool ↗Frequently asked questions
Base64 decoder
questions.
Why does the decoder say my input is invalid?
Characters outside the Base64 alphabet, or a length that cannot be padded, mean the string was cut off or is not Base64 at all. Whitespace is ignored.
Does it handle URL-safe Base64?
Yes. Hyphens and underscores are treated as their standard equivalents, so tokens from JWTs and query strings decode correctly.
Is anything I enter saved or sent to Form Koi?
No. Everything you type or upload stays in this browser tab and is processed locally. Copy or download anything you want to keep before leaving the page.
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