Full Unicode support
Accented letters, Cyrillic, Arabic, Chinese, Japanese and emoji are all encoded correctly using UTF-8.
Base64 Encoder & Decoder
Encode text to Base64 or decode Base64 back to readable text instantly. Full Unicode support means accented letters, non-Latin scripts and emoji are handled correctly. No sign-up, no tracking, no data sent to a server.
Base64 encoder and decoder tool
Private by design. All encoding and decoding run locally using the native btoa(), atob(), TextEncoder and TextDecoder APIs. Your text is never uploaded, stored, or logged.
Input
Output
Status: Waiting for input
Last action: —
Size change: —
Base64 is an encoding, not encryption. Anyone with the string can decode it back to the original text. Do not use it to hide passwords or secrets.
How to use the Base64 encoder and decoder
- Paste your input. Type or paste plain text into the left panel to encode, or paste a Base64 string to decode.
- Click Encode or Decode. Encode converts text to Base64. Decode converts Base64 back to readable text.
- Review the output. The result appears in the right panel. Invalid Base64 produces a clear error with an explanation.
- Copy or swap. Use Copy output to put the result on your clipboard, or Swap to copy the output back into the input panel for a second pass.
- Clear when done. Click Clear to empty both panels, especially on a shared computer.
Key features and benefits
Instant encoding
Click Encode or Decode and the result appears immediately, with no page reload.
Clear error messages
Invalid Base64 produces a helpful explanation, so you know exactly why decoding failed.
Fully private
Everything runs in your browser using native JavaScript functions. Nothing is transmitted or logged.
Swap panes
Move the output back into the input with one click, so round-tripping is a single gesture.
Responsive layout
Side-by-side panels on desktop, stacked panels on mobile — comfortable on any screen size.
Privacy and limitations
- Fully client-side. Every operation runs in your browser using native JavaScript functions. No text is ever uploaded, stored, or logged.
- No tracking of content. The tool does not record what you paste. There is no analytics on input or output.
- Not encryption. Base64 is a reversible encoding. It hides nothing from anyone who has the string. Never use it to protect passwords or secrets.
- No automatic saving. Content is not persisted between visits. Reloading the page clears both panels.
- Text only. This tool handles text and UTF-8 encoded bytes. For binary files such as images or PDFs, you need a dedicated file-to-Base64 converter.
Frequently asked questions
What is Base64?
Base64 is a way of representing binary data using only 64 printable ASCII characters. It is commonly used to embed images or files inside text-based formats like JSON, HTML or email, and to safely transmit binary content through systems that only accept text.
Is Base64 encryption?
No. Base64 is an encoding, not encryption. It is fully reversible and provides no secrecy. Anyone who has the Base64 string can decode it back to the original data. Do not use it to hide passwords or secrets.
Does this tool support Unicode and emoji?
Yes. The tool uses the native
TextEncoder and TextDecoder APIs to convert text to UTF-8 bytes before encoding to Base64, and to decode those bytes back to UTF-8 on the way out. This means accented letters, non-Latin scripts and emoji are handled correctly.Is the Base64 encoder safe to use?
Yes. Everything runs in your browser using native JavaScript. Your text is never uploaded, stored, or logged on any server.
Why does decoding sometimes fail?
Base64 strings must use only the letters A to Z, a to z, digits 0 to 9, the plus sign, the forward slash, and the equals sign for padding. Whitespace is usually ignored but other characters will cause decoding to fail. The tool shows a clear error message if the input is not valid Base64.
What is the difference between standard and URL-safe Base64?
Standard Base64 uses
+ and / characters, which have special meaning in URLs. URL-safe Base64 replaces + with a hyphen and / with an underscore. This tool accepts both forms when decoding.A practical guide to Base64 encoding
Base64 shows up constantly in modern software, often without any explanation of what it is or why it exists. You see it in data URLs for inline images, in JSON Web Tokens, in HTTP Basic authentication headers, in email attachments, and in any situation where binary data needs to travel through a channel that only accepts text. Understanding what Base64 does and does not do is essential for anyone working with web APIs, authentication, or configuration files.
What Base64 actually does
Base64 takes a sequence of bytes and rewrites it using 64 printable ASCII characters: the uppercase letters A–Z, the lowercase letters a–z, the digits 0–9, the plus sign + and the forward slash /. Because each Base64 character carries six bits of information, four Base64 characters represent exactly three bytes of input. If the input length is not a multiple of three, the encoder pads the output with one or two equals signs = to keep the length aligned.
Why Base64 is not encryption
Every Base64 string can be decoded back to the original bytes by anyone who has it. There is no key, no password, and no secret involved. A common mistake is to assume that an encoded password or API key is now safe because it is unreadable at a glance. It is not. Treat Base64 strings exactly as you would treat the original data — because anyone who intercepts them can decode them in a fraction of a second.
Unicode and the UTF-8 bridge
The browser's built-in btoa() and atob() functions work on binary strings, meaning they interpret each character as a single byte. This breaks for any character outside the ASCII range. The correct approach — used by this tool — is to convert the text to UTF-8 bytes with TextEncoder first, then encode those bytes to Base64. On the way back, decode the Base64 to bytes and use TextDecoder to interpret those bytes as UTF-8. This is what makes emoji and non-Latin scripts round-trip correctly.
Standard vs. URL-safe Base64
Standard Base64 uses + and /, which have special meaning in URLs and filenames. When a Base64 string needs to appear inside a URL — for example, in a JSON Web Token or a query parameter — the + is replaced with a hyphen - and the / with an underscore _. Padding is often stripped as well. This variant is called base64url. The tool on this page accepts both forms when decoding, so you can paste either style without worrying about which one a system produced.
Common pitfalls
- Assuming secrecy. Base64 hides nothing. Use real encryption like AES or a TLS connection when confidentiality matters.
- Forgetting to strip whitespace. Some APIs insert newlines every 76 characters, following the MIME standard. This tool ignores whitespace automatically, but other decoders may not.
- Mixing URL-safe and standard characters. A string that contains both
+and-is ambiguous. Decode it in the mode that matches how it was produced. - Using it for large binaries. Base64 expands data by about 33%. For large files it is often better to send binary directly than to Base64-encode it.
About this tool
This Base64 encoder and decoder is part of the TempScript free online tools collection. It runs entirely in your browser, requires no account, and never sends your data anywhere. If you work with APIs and text regularly, you may also find our URL encoder and decoder and JSON formatter useful for quick formatting tasks.
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