Base64 Encoder/Decoder

You found a Base64 string and need to know what it says

Base64 turns up all over technical SEO work: in tracking and redirect parameters, inline images in CSS, token payloads, and API responses. It also comes in handy the other way, when a system only accepts plain ASCII. This converter handles both directions for text. It treats input as UTF-8, so non-English characters are preserved, and the conversion happens locally without sending your data to a server.

Step by step

1. Put the text or the encoded string into the Input area.
2. Choose the direction yourself: Encode → produces Base64, ← Decode produces readable text.
3. Check the Output area below the buttons. You cannot type into it; it only shows results.
4. Use Copy Result to grab the converted value.

What to watch for

The decoder only accepts standard Base64, the alphabet that uses plus and slash. The URL-safe variant, used by JSON Web Tokens among others, replaces them with a hyphen and an underscore, and pasting it here produces an error. Replace hyphens with plus signs and underscores with slashes, then try again. Line breaks in wrapped Base64 are ignored by modern browsers, so those are usually not the problem.

Decoded bytes must form valid UTF-8 text. If the string holds a PNG, a PDF or compressed data, the decoder cannot display it and shows the same invalid-string alert, which can be misleading. For binary files, use a tool that saves the output as a file.

Encoding grows the data: four output characters for every three input bytes. That overhead matters if you are thinking of inlining images or fonts, since the larger text cannot be cached separately from the file that contains it.

Questions people ask

Is Base64 a way to hide or secure data?

No. It is a reversible representation with no key. Treat Base64 text exactly like the plain text it contains.

Can I convert an image to a data URI here?

No. The input is a text box, with no file picker. Encoding an image requires reading its raw bytes, which this page does not do.

Why do I get "Invalid Base64 string" on a value I know is valid?

Either it uses the URL-safe alphabet, or it decodes to binary data rather than text. Both produce the same message here.

Further reading: Missing Charset Declaration: How to Fix It and URL Parameter Handling for SEO: When to Block, Canonicalize, or Let Google Crawl.

The same tool is also published on the static mirror at seoprocheck.github.io, and the rest of the set is on the free tools page.