Base64 Decode
This free online Base64 decoder turns Base64 strings back into readable text the moment you paste them.
How to use
- Paste the Base64 string you want to decode into the editor below.
- The decoded text appears instantly; invalid input is reported clearly instead of decoded into garbage.
- Copy the result — it was produced on your device and never left your browser.
Frequently asked questions
Why do I get an "invalid base64" error?
The decoder is strict so bad input never becomes silent corruption: characters outside the standard alphabet (A-Z, a-z, 0-9, +, /, =), a length that is not a multiple of four, or broken padding all fail with a clear message. Line breaks and spaces are not the problem — they are stripped automatically — so check for URL-safe characters or a truncated copy instead.
Do I need to strip line breaks or add padding first?
No. Whitespace and line breaks are removed automatically before decoding, so PEM-style text wrapped at 76 columns and multi-line attachments decode as-is. Input must be standard, correctly padded base64 though: unpadded strings such as raw JWT segments and URL-safe variants (- and _) are rejected with an explicit message.
My Base64 contains - and _ instead of + and /. Can you decode it?
That is the URL-safe variant, which this tool rejects on purpose to avoid ambiguity. Replace the minus signs with + and the underscores with / (and add = padding to a multiple of four if missing), then decode — the bytes are the same.
The decode succeeded elsewhere but shows garbage here — why?
Your bytes are probably not UTF-8 text: they may be a binary file, a legacy encoding like GBK, or encrypted data. This decoder fails explicitly on non-UTF-8 bytes rather than printing mojibake, which is a signal about the data, not a bug.
Is it safe to decode sensitive strings here?
Yes — decoding runs locally in your browser. Tokens, credentials and private payloads never leave your device, are never stored or logged, and are gone when you close the page.
Related tools
About this tool
This free online Base64 decoder turns Base64 strings back into readable text the moment you paste them. It is built for reading credentials from a decoded basic-auth header, inspecting the payload section of a JWT while debugging auth, recovering the text inside a data URL, and checking what a configuration value actually contains before you trust it. The decoder is UTF-8 aware: decoded bytes are validated as UTF-8 text, so "SGVsbG8g5LiW55WM" comes back as "Hello 世界" instead of mojibake. Equally important is what it refuses to do: input containing characters outside the standard Base64 alphabet, a length that is not a multiple of four, or bytes that are not valid UTF-8 produces a clear error instead of a silently corrupted result — with Base64 you always want to know when something is wrong, not receive plausible-looking garbage. Decode happens entirely in your browser: tokens, credentials and private payloads are processed locally on your own device and never uploaded, stored or logged. Paste your Base64 below and read the original text.