How do I decode a Base64 string?

Paste it into the box and the decoded UTF-8 text appears instantly. The tool maps each group of 4 Base64 characters back to 3 bytes and decodes them as text.

Does it handle URL-safe Base64?

Yes. The decoder accepts both the standard +/ alphabet and the URL-safe -_ alphabet, converting - to + and _ to / before decoding.

What if my Base64 is missing its = padding?

The decoder restores padding automatically based on the string length, so unpadded Base64 (common in JWTs and URLs) still decodes correctly.

Why do I get an invalid input error?

The string contains characters that are not valid Base64, or its length leaves a single leftover character that cannot form a byte. Stray spaces, truncation, or non-Base64 text are the usual causes. Invalid UTF-8 byte sequences are also flagged.

Can it decode Base64 that is not text, like an image?

This tool decodes the bytes and shows them as UTF-8 text, so binary payloads such as images will not be readable here. For images, use a Base64-to-image tool instead.

No. Decoding runs entirely in your browser with built-in APIs — nothing is transmitted anywhere.

Base64 Decoder — Gera Tools

Base64 decoder

Turn a Base64 string back into readable text. The decoder accepts both the standard and URL-safe alphabets, fixes missing padding for you, and decodes the bytes as UTF-8 — useful for inspecting JWT payloads, data URIs, config values and email headers.

How it works

First the tool normalises the input: URL-safe characters - and _ are converted back to + and /, and any missing = padding is restored so the length is a multiple of 4. It then uses the browser’s built-in atob to turn each group of 4 characters into 3 bytes, and decodes those bytes with a strict UTF-8 decoder. If the bytes are not valid UTF-8, or the length is malformed, it reports an error rather than returning garbage.

Example

Decoding SGVsbG8sIEdlcmEgVG9vbHMh:

SGVsbG8sIEdlcmEgVG9vbHMh → Hello, Gera Tools!

Base64	Decoded text
`R2VyYQ==`	`Gera`
`SGk=`	`Hi`

To encode in the first place, use the Base64 encoder. All decoding happens locally in your browser — nothing is uploaded.