How to Decode Base64 and Fix Decoding Errors

Step-by-step

Paste the Base64 string into the tool and choose decode.
Remove any prefix such as data:image/png;base64, if it is part of the pasted text.
Check the result. If it is binary data such as an image, it will not look like readable text.
If decoding fails, check for spaces, line breaks and characters outside A to Z, a to z, 0 to 9, + and /.
If the string uses - and _ instead of + and /, it is URL-safe Base64 and needs to be converted first.

Why decoding fails

The usual causes are characters that are not part of the Base64 alphabet, a string that was cut short, or missing padding. Some decoders require the length to be a multiple of four, so add = characters at the end until it is.

Readable text or random symbols

If the decoded text shows strange characters, the original text probably used UTF-8 and was read with a different encoding. If the result is binary, such as a PDF or image, it is not meant to be read as text.

Decoding is not a security check

Anyone can decode Base64. If you find a password or token in Base64, treat it as exposed in plain text.

USE THE TOOL

Finish the task with DevUtilityKits

Use the relevant online utility, check the result, and continue with your development workflow.

Open Base64 Encoder and Decoder →

Frequently asked questions

Why does Base64 decoding say the input is invalid?

The string likely contains characters outside the Base64 alphabet, extra spaces or line breaks, or it is cut short.

Do I need the padding characters?

Some decoders require them. If decoding fails, add = at the end until the length is a multiple of four.

Why do I see strange characters after decoding?

The text was probably encoded as UTF-8 and read as another encoding, or the data is binary and not text.

Can I decode an image from Base64?

Yes, if the Base64 holds image bytes. Remove any data: prefix first, then use a tool that turns the bytes back into an image.