Base64 Decoder — Decode Base64 to Text Online
Decode standard Base64 strings back to readable UTF-8 text in seconds. Paste a token, press decode, and get the original text — with honest errors when the value is not valid Base64, and no upload of anything you paste.
Privately decoded in your browser — the value never leaves this tab.
Decoding happens entirely in this tab with the browser’s built-in atob() and a UTF-8 decoder. The value you paste never leaves your device — there is no fetch, form, beacon or log containing it.
What it supports
- Input: standard Base64 (A–Z, a–z, 0–9, +, /) with optional padding.
- Accepts line-wrapped Base64 — surrounding whitespace is stripped first.
- Output: UTF-8 text (or a clear error when the bytes are not valid UTF-8 text).
How it works
- 1
Paste the Base64
Paste any standard Base64 string, including line-wrapped values from editors or email.
- 2
Decode locally
Click Decode. Validation and conversion happen entirely in this tab.
- 3
Copy or download
Copy the decoded UTF-8 text or download it as a .txt file.
What this tool does
This decoder takes a standard Base64 string, validates it, removes the whitespace that editors add when wrapping long lines, and converts the bytes back to UTF-8 text. Invalid input is never silently re-interpreted: if the alphabet or padding is wrong, or the token uses the URL-safe variant, you get an explicit, readable error.
Who it is for
Developers decoding JWT payload segments, SMTP and XML snippets, emails with quoted-printable-style attachments, and support engineers inspecting Base64 values users paste into tickets — without sending the data to a third-party service.
Using the decoder
Paste or type the Base64 value, click Decode, and the UTF-8 text appears with one click of Copy or a Download as .txt. Long wrapped values work as-is; the decoder strips the wrapping whitespace before validating.
When decoding fails
A value that ends in - or _ is URL-safe Base64, which is a different alphabet — this tool errors on it rather than guessing a translation. Values with wrong padding, stray characters, or length not divisible by four are invalid Base64 and are rejected too. Finally, bytes that do not form valid UTF-8 text are reported as such, because showing garbage would only hide the real problem.
Limits & notes
- Standard Base64 only. URL-safe tokens containing - or _ are rejected with an explicit message (see the FAQ).
- Decoded output is capped at 15 MB so a pasted mega-bundle cannot freeze your tab.
- If the decoded bytes are not valid UTF-8, the tool tells you instead of showing mojibake — use the Base64 to Image tool for binary payloads.