Base64 Decoder

Decode a Base64 string back into readable text. Paste the Base64 and the decoded, UTF-8 aware result appears instantly, with a clear warning if the input is not valid Base64. Decoding runs entirely in your browser.

Base64 Input

Decoded Text

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Why use Base64 Decoder?

Decoding Base64 turns that wall of letters and digits back into the original text or data. Because Base64 appears everywhere, in JWT segments, data URIs, email MIME parts, and API payloads, being able to peek at what a string actually contains is a daily need for developers. This decoder is UTF-8 aware, which matters: a naive atob call interprets bytes as Latin-1 and corrupts anything outside basic ASCII. The tool reconstructs the original UTF-8 sequence, so non-English text and emoji come back intact. If you see the invalid-input warning, the usual culprit is URL-safe Base64. That variant swaps + and / for - and _ so the string is safe in URLs; convert those two characters back and it will decode. Like the encoder, everything happens locally, so you can safely inspect tokens and payloads without sending them anywhere. The input is trimmed of surrounding whitespace before decoding, so a value copied from a wrapped log line still decodes cleanly, a quick way to check the middle segment of a JWT, which is just Base64url-encoded JSON.

Key benefits

UTF-8 aware decoding restores accented characters and emoji correctly
Clear "Invalid Base64" message when a string cannot be decoded
Instant, live decoding with one-click copy
Client-side, the string you paste is never uploaded

Features

Decodes standard Base64 and reports invalid input
Reconstructs UTF-8 text rather than mangling non-ASCII bytes
Trims surrounding whitespace automatically

Popular use cases

Reading a Base64 value pulled from JSON, a log, or a config file
Inspecting the contents of a data: URI
Checking what an encoded token or header actually contains
Verifying that an encode/decode round-trip is lossless

How to use Base64 Decoder

1
Paste the Base64
Paste your Base64-encoded string into the input box.
2
Read the decoded text
The decoded text appears instantly; invalid input shows a clear warning instead.
3
Fix invalid input if needed
If you see "Invalid Base64 string", check for URL-safe characters (- and _) or missing padding, convert them to standard Base64, and paste again.
4
Copy or clear
Click "Copy Text" to copy the decoded output, or "Clear" to reset.

Frequently asked questions

Why does it say my Base64 is invalid?

Common causes are URL-safe Base64 (which uses - and _ instead of + and /), missing or wrong padding (= characters), or stray characters and line breaks. Standard Base64 with correct padding decodes cleanly.

Does it handle URL-safe Base64?

It targets standard Base64. If your string is URL-safe, replace - with + and _ with / first, then decode.

Can it decode emoji and non-English text?

Yes. The decoder interprets the bytes as UTF-8, so non-ASCII content is restored accurately rather than shown as garbled characters.

Can I decode a data: URI directly?

Paste only the Base64 portion after the comma in a data: URI, not the "data:image/png;base64," prefix itself, since that prefix is not part of the encoded data.

Is the decoded data private?

Yes. Decoding happens entirely in your browser; the string you paste is never transmitted.

Related guides

Base64 Explained: What It Is, What It Isn't (Not Encryption)

Last reviewed: July 2026

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