Base64 Decoder

Decode Base64 encoded strings back to plain text

What is it and how does it work?

A Base64 decoder turns Base64-encoded text back into the original data it represents. Base64 is a way of writing any data — text, an image, a file — using only 64 safe characters (A–Z, a–z, 0–9, + and /), so it can travel through systems that only handle plain text, such as URLs, email bodies, JSON fields and HTML attributes. Decoding reverses that: you paste the encoded string and get back the readable text or the raw bytes that were encoded in the first place.

It is important to understand what Base64 is not: it is encoding, not encryption. Anyone can decode it, so it provides no secrecy — it only makes binary data survive a text-only channel intact. That is exactly why you reach for a decoder so often when debugging: a data URI in CSS, the payload of a JWT, a header value, or an email attachment block all use Base64, and decoding lets you read what they actually contain. This tool decodes in your browser, so the data never leaves your machine.

Common use cases

• Inspecting a JWT: decode the Base64url payload of a token to read its claims while debugging authentication.
• Reading a data URI: decode the Base64 part of a data: URL to recover the text or inspect the embedded content.
• Debugging an API or email: decode a Base64 header value or message part to see the original text it carries.

Frequently asked questions

Is Base64 a form of encryption?

No. Base64 is reversible encoding with no key and no secrecy — anyone can decode it instantly. It exists to carry binary data safely through text-only channels, not to protect it. Never use it to hide passwords or sensitive information.

What do the trailing = signs mean?

They are padding. Base64 works in groups of four characters, so one or two = signs are added at the end to fill out the final group when the original data does not divide evenly. A correct decoder handles them automatically.

Why does my decoded text look like gibberish?

Base64 often encodes binary data — images, compressed files, encrypted blobs — that is not readable text. If the result looks like noise, the original was probably not plain text. Text decodes cleanly only when the source was text in a compatible character set.

What is the difference between Base64 and Base64url?

Base64url is a URL-safe variant that replaces + and / with - and _ so the string is safe inside URLs and tokens like JWTs. The content is the same; a robust decoder accepts both forms.

Developer

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