Base64 decoder

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About the Base64 Decoder

The Base64 Decoder reverses Base64-encoded strings into their original text or binary form. It works entirely in your browser.

How to use it

Paste Base64 text. The decoded output appears below. Switch between text and binary mode as needed.

Common use cases

Decoding data URLs. Inspecting HTTP Basic Auth headers. Reading JWT segments.

What is Base64 Decoding?

Base64 decoding is the reverse operation of Base64 encoding, turning a string of 64-character alphabet symbols back into the exact bytes they originally represented. Whenever an application or an email embeds binary content as readable text, that text must be undone before the underlying data can be used again. This tool performs that reversal as you paste, rebuilding the original text, image, or file byte by byte. Because the transformation is lossless, a properly formed Base64 string always yields the precise original content, with no rounding, trimming, or corruption along the way. Decoding is a routine step in data pipelines, web development, and debugging, where encoded strings appear frequently in logs, API responses, and configuration files.

How to Use

Paste any Base64 string into the input box and the decoded result appears immediately, with no button to press. Text content shows up directly in the output panel, while binary output such as an image or a PDF can be saved as a separate file using the download option. Use the copy button to capture the decoded text to your clipboard for use elsewhere. If the string uses the URL-safe alphabet with dashes and underscores instead of plus and slash, choose that variant so the tool interprets the characters correctly. Everything happens locally in your browser, and the input clears instantly whenever you start a new item.

Common Use Cases

Security researchers and developers decode payloads to inspect what a hidden string actually contains, which is especially helpful when auditing logs or reviewing network traffic. Web professionals decode data embedded inside front-end code to recover images and small files without fetching them separately. Base64 decoding is equally useful for recovering the original content of an encoded email attachment, reading configuration tokens, or unwrapping JSON values that were safely quoted for transport. In short, any time an encoder has made binary data readable as text, this tool returns it to its true, usable form.

Frequently asked questions

Does decoding reveal secure or encrypted data?

No. Decoding only reverses an encoding, and it cannot unlock anything that was encrypted with a key. If the original content was encrypted before it was encoded, the decoded output will still be unreadable ciphertext. Base64 decoding recovers an exact prior representation, nothing more.

Can I decode binary files like images and PDFs?

Yes. When the decoded result is binary rather than plain text, the tool lets you download it as a file so the image, document, or archive is saved in its original format. This makes it simple to recover files that were embedded as Base64 in emails or API responses.

Why do I sometimes see garbled output?

Garbled or empty output usually means the input is not a valid Base64 string, or contains whitespace, line breaks, or characters outside the expected alphabet. Removing stray spaces, confirming the correct variant, and ensuring the string is complete usually fixes the issue.

Is my pasted string stored anywhere?

No. Decoding happens entirely in your browser, and the string you paste never travels to a server or gets written to any log. Your content stays private and local to your device.