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Base64 Decode
Paste Base64 and read the decoded text instantly, or download the decoded file. URL-safe Base64 works too.
Decoded data looks like a file
Runs in your browser. Your data is never sent to a server.
How to use the Base64 Decode
Paste the Base64
Paste a Base64 string, a URL-safe value or a full data URI. Spaces and line breaks are ignored.
Read the result
Text is decoded as UTF-8 as you type. If the data is a file, such as an image or PDF, the tool tells you its type and size.
Copy or download
Copy the decoded text or download the file with the right extension.
Why use this tool
Base64 turns binary data into plain letters and digits so it can travel through email, JSON, URLs and HTTP headers. You meet it in API tokens, email attachments, Kubernetes secrets, data URIs and basic authentication headers, and you need a quick decoder to see what is inside.
This online Base64 decoder tool handles the variants that trip up simple decoders: URL-safe Base64 with - and _, values with missing = padding, line-wrapped MIME output and data URIs with a data:…;base64, prefix. Text is decoded as UTF-8, so accented letters, Cyrillic and emoji come out correctly.
Frequently asked questions
How do I decode Base64?
Paste the Base64 string into the box. The decoded text appears immediately; if it is a file, you can download it instead.
Why do I get an invalid Base64 error?
The string contains characters outside the Base64 alphabet or was cut off. Check that you copied the whole value; spaces, line breaks and missing padding are fine.
How do I decode Base64 in JavaScript?
For text use new TextDecoder().decode(Uint8Array.from(atob(b64), c => c.charCodeAt(0))). Plain atob() alone breaks non-English characters.
How do I decode Base64 in Python?
base64.b64decode(s).decode("utf-8"). For URL-safe strings use base64.urlsafe_b64decode and add = padding if needed.
Are my files uploaded to a server?
No. formatmath converts files with code that runs inside your browser. Your files are never uploaded, stored or seen by us.
Is it free?
Yes. There is no watermark and no daily limit. An account is optional and only keeps a history of your conversions.