Base64 Decoder
Paste a Base64 string to see what it contains. Text is shown immediately; images are previewed; any other binary data can be downloaded as a file.
- Runs in your browser
- No sign-up
- Free to use
Decoded file
How to use Base64 Decoder
- Paste the Base64 string, or a complete data URI, into the input.
- The decoded text appears on the right as you type.
- If the data is an image or another binary file, a preview or file summary is shown instead.
- Copy the decoded text or download the decoded file.
Base64 Decoder features
Tolerant input handling
Accepts standard and URL-safe alphabets, missing padding, line breaks and whitespace.
Data URI aware
Strips the data:…;base64, prefix automatically and uses its media type.
Binary detection
Recognises images, PDFs, ZIP archives and other formats from their signature.
Image preview
Decoded PNG, JPG, GIF, WebP and SVG images are displayed straight away.
Download as file
Save decoded binary data with the correct file extension.
Private
Decoding happens in the browser, so tokens and credentials are not sent anywhere.
When to use Base64 Decoder
- Reading the contents of a Base64 value found in a config file, log or API response.
- Recovering an image embedded as a data URI in HTML or CSS.
- Checking what a Basic Authentication header contains.
- Inspecting an encoded attachment or certificate.
Base64 Decoder FAQ
Why do I see strange characters in the output?
The Base64 probably encodes binary data, such as an image or a compressed file, rather than text. The tool detects common formats and offers a download; otherwise the bytes are shown as text as best they can be.
What does “Invalid Base64” mean?
The input contains characters outside the Base64 alphabet, or its length cannot correspond to whole bytes. Check that nothing was cut off when copying and that it is not a different encoding such as hexadecimal.
Does it handle Base64 without = padding?
Yes. Missing padding is restored automatically, which is common in URL-safe Base64 such as JWT segments.
Is it safe to decode secrets here?
Decoding runs locally and nothing is transmitted. As with any web tool, avoid pasting production secrets on a shared or untrusted computer.
Which text encoding is assumed?
UTF-8, which is what virtually all modern systems use. Text encoded with a legacy code page may show replacement characters.
Reading Base64 data
Decoding reverses the encoding process: each character is mapped back to its six-bit value, the bits are regrouped into bytes, and padding is discarded. The result is a sequence of bytes, and what those bytes mean depends on what was encoded in the first place.
If the bytes form valid UTF-8, this tool shows them as text. Otherwise it looks at the first few bytes for a signature: PNG files begin with the bytes 89 50 4E 47, JPEGs with FF D8 FF, PDFs with %PDF and ZIP-based files with PK. Recognising the format lets it preview images and suggest the right extension when you download the file.